Sunday, 20 August 2017

The Essence of Go

The Go programming language - what do you know about it? I was looking for my next favorite language a couple of years ago.  I tried and rejected Go based on a fair bit of research. However, I have been working on a project for the last few months using Go and I must admit my initial impressions were wrong. Here I hope to describe what using Go is really like for anyone thinking of trying it so they don't jump to the same erroneous conclusions that I did.
“… what using Go is really like …”

Last year I mentioned here another new language, Rust, that I am very excited about (and which I hope to talk more about soon). Go is similar to Rust in many ways but Go is not a low-level language like Rust (despite what Google and others say). I would classify Go as a medium-level language on a par with C#. For one thing a language can't be low-level unless it allows control of memory allocations, but Go (like C#, Java and many interpreted languages) uses GC - ie, memory management is handled by the run-time using a garbage collected heap (I might talk more about that later).

Initially I decided to steer clear of Go, for several reasons but mainly due to its lack of support for templates (generics) - which BTW Rust does have. But now that I have used Go I think one particular aspect is brilliant - it makes programming simple (in a myriad of ways), even more so than C# (which I talked about last time).  And if you have read much of my blog you may have noticed my love of simplicity. I believe complexity is at the root of all problems in software development (see my very first post Handling Software Complexity).


Whenever I try a new language I quickly get a feel for its style - what the designer(s) think is important (performance, flexibility, safety, etc). I can also usually pick what other languages influenced it. But Go's style and influences confusing.
Go's style and influences are confusing

First, it's overriding premise seems to be to keep things simple (and most of the time it does that very well), but the motivation for this is a mystery. The initial impression I got was that it was that everything was done "on the cheap" - that is, the Go creators just found it too hard, or too time-consuming, to think about adding exception handling or templates or whatever. This is clearly wrong when you consider some of the other features that are present. I next formed the opinion that it was based on an intense dislike of C++, so anything that Bjarne Stroustrup invented was simply rejected out of hand. My current (final?) impression is that the creators of Go consider the average programmer to be lazy and incompetent so everything is kept as simple and safe as possible (though sometimes making things safer detracts from simplicity as we will see).
“ …making things safer detracts from simplicity…”

Go's influences are many but as a generalization I would say that Go is a bit like a simplified C#, with all the C++ derived stuff removed, plus some additional features that support concurrency. For example, it has features similar or the same as these from C#: GC (memory management), lambdas (called closures in Go), metadata, reflection, interfaces, zero initialization, immutable strings, partial classes, extension methods, implicit typing (var), etc. And like C#, Go also tries to avoid lots of the problem areas of C/C++ such as expressions with undefined behavior.

Go is like C# with the C++ stuff removed
On the other hand almost all the things that C# inherited from C++  Go completely discards - like generics, exception handling, operator overloading, implicit conversions, and even classes and inheritance.

However, there are a few more things to Go that seem to be new or come from elsewhere.  One of the most interesting is its support for concurrency, including channels which I first encountered in Occam about 25 years ago. And, of course, like all popular modern languages Go is heavily influenced by C and C++ (though in the case of C++ the influence is in the form of avoidance).  Let's look at these influences just a bit more.

Safer C

Go has strong links to C, ostensibly because Google wanted a modern alternative to C. I think a big reason is that one of the Go architects is Ken Thompson who (along with Dennis Ritchie) created the C language (and the Unix operating system) and even precursors to C in the 1960's.

The syntax of Go is obviously derived from C, but there are many "improvements" to avoid problems that many beginners in C encounter. A good example is that there is no automatic "fall through" between cases in a switch statement which is a perennial source of bugs in C. On the other hand side-effects in expressions have been removed (eg, no assignment chaining etc) which is bad (see below).

Most of the problems with using pointers that C is notorious for have been eliminated by disallowing pointer arithmetic and by automatic memory handling using the garbage-collected heap.

Another common problem for beginners in C is due to uninitialized variables which can lead to bugs which are almost impossible to track down due to unreproducibility. Go's solution is the "shotgun" approach where everything is guaranteed to be initialized to a "zero" value.  This is good for reproducibility but introduces its own problems as I discussed in Shotgun Initialization.

Finally, I should mention that Go tries to address perhaps the worst problem of most C code (yes worse than the above problems!). This is the problem that there is an enormous amount of C code that ignores error conditions or does not handle them correctly. Go has a more systematic approach to error handling but, in all honesty, it is only marginally better than the C approach. Now I am not saying that Go should have exceptions and I understand and agree with the decision not to have them (even though it effectively does have them in the form of panic/recover). All I am saying is that Go should do something about relieving the tedium and complexity of C-like error-handling and in fact I have a proposal to do just that - more on this later.
“Go error-handling is
only marginally better than C”

In summary, the designers of Go have honored the age-old tradition of finding ways to improve on C.  Some of the improvements are actually useful but some are just denigrating to competent programmers.


Go is the first language I have encountered since Occam to use the brilliant idea of communication between concurrent processes using "channels".  Apparently channels are heavily used in Erlang and other languages that I have not had the fortune to use.  However, at one time (more than 25 years ago) I was very interested in the Inmos Transputer which you can read more about here but basically it was designed to allow multiple CPUs to be hooked together easily.

Occam had other features which I thought were going to be very important such as the ability to say whether instructions could be parallelized or must be run sequentially.
I became interested in the Transputer as it was a little like my own (even more way-out) idea for a bit-oriented processor. At the time single chip CPUs were 8 or 16 bit.

My thinking was that there large benefits in moving to single-bit processors which read from memory, and other CPUs serially - ie, one bit at a time.  Each CPU would be like a neuron. They could be hooked together to make something more powerful.

The industry successfully advanced in the opposite direction and soon 32-bit processors (and now 64-bit CPUs) are the norm. I'm not sure that this was the right direction. Maybe one day single-bit computers will find a place.

At the time I thought the software industry needed to embrace multi-threading (or multi-tasking as it was called then). At the time even the major operating systems from Microsoft and Apple did not support multi-tasking (using a kludge called "co-operative multi-tasking). Unfortunately, it was another decade before mainstream operating systems and languages were supporting multi-threading.

It's a shame that the Transputer and Occam never became popular. I think they were ahead of their time.

Not C++

As I said above I think one of the main influences on Go is that it avoids anything invented by C++. Here is a list and my opinion of whether that is good or bad.
  1. No support for inheritance, ie. no vtables etc, as used in compiled OO languages. This is not a bad thing, since inheritance is over-used, badly used and even when used well there are simpler alternatives. When required, Go has mixins (struct embedding) and interfaces, which are perfectly adequate.
  2. No templates. Templates (which made possible the amazing STL) are the thing I like most about C++.  This is a bad thing.
  3. No exceptions. I appreciate the argument for no exceptions, but I wish the alternative provided by Go was better. (Rust has no exceptions, but handles errors better using algebraic data types.) Go tries to improve on C's error-handling (which is very bad) but it is almost as easy to ignore errors in Go as C and the tedium of creating masses of error-handling code is back. Not being one to simply criticize, I propose how to improve Go's error-handling below.
  4. “I propose how to
    improve Go error-handling”
  5. No namespaces. Go has a similar concept of packages (sort of like a combination of assembly and namespace of C#). Unfortunately, packages can't be nested, which is limiting.
  6. Const was one of the simplest and most brilliant inventions of C++. I can't believe Go (and other modern languages) even consider leaving it out.
  7. No public/private/protected keywords. Go has a system where capitalized variable names are public, but a lower-case first letter means it is private to the package (a bit like internal in C#). This is simple but I am undecided whether it is sufficient.
  8. No user-defined operator-overloading. (Of course, like most languages there is operator-overloading for built-in types.) I don't really miss this.
  9. No function overloading (except you can overload methods with different receiver types - otherwise interfaces would not work). I miss this ability but I guess it is not essential.
  10. No optional parameters. I understand the problems of optional parameters, but they are rarely seen in practice. Not a biggy but the alternatives in Go are all error-prone and/or tedious to implement.
  11. Go eschews the C++ philosophy that you should be able to create user-defined types that are as simple and flexible to use as the built-in types (eg see 7 above). Some people hate this about Go, but personally I am not that fussed as long as it gives me everything I need to do the job simply and effectively (which it usually does)
  12. There is nothing as flexible and useful as the STL.  This is bad.
  13. One thing Go does use that comes from C++ is the // end of line comments. (Maybe the Go designers were not aware where that came from :)
In summary, leaving all the C++ stuff out greatly simplifies things (and I don't like a lot of the complexity of C++ either, as you may have guessed from some of my previous posts). However, I think the designers of Go may have thrown out the baby with the bath-water. In particular, I think templates (generics) and const are essential for any modern language.


Leaving out lots of features found in C++ and other languages makes Go programming simpler, but there are a lot of other niceties. Here is a list of all the things I like about Go.
  • Simple Builds Probably the best thing about Go is how easy it is to build a project. In the past (on C projects) I have spent hours or even days trying to sort out problems with header file inclusion, linking or even run-time problems due to incompatible struct member alignment, not to mention DLL Hell. C++ improved on C by using name-mangling so the linker could catch many mistakes. Then C# (actually .Net) further alleviated build problems using metadata to completely describe how to attach to an assembly. Go takes this a step further and makes building software quick, painless and trouble-free.
  • Integration I have always found integrating an open-source library into my own project or even downloading and building a complete application time-consuming and frustrating. (For example, I have spent weeks trying to streamline the build process for my own project which uses several open-sources libraries - see HexEdit.) In Go you simply use go get which finds and installs an open-source project and dependent projects so you can start using it straight away.
  • Compilation Speed Go's build speed is amazing (mainly because the metadata for a package also stores all info about its dependent packages). I never used to think build speed was that important since you can take a break while the project is building. However, Go's almost instant builds makes things possible like the IDE checking your code for all errors (not just syntax errors) as you type, which is great.
  • Type Safety Because of the quick build speed developing with Go has the feel of using an interpreted language like Python. The problem with an interpreted language, though, is that a lot of errors aren't found until you run the program. Go on the other hand catches many errors at compile-time resulting in greater confidence that the code will run without error.
  • Memory Management Another huge tedium in many C programs is keeping track of heap memory and knowing who has to free it. And, if you get it wrong then you can have memory-leaks, double-frees and even nastier problems such as overwriting memory that is used for something else. Go avoids all of this by using a garbage collected heap while somehow avoiding any major performance hit. (My guess is it makes typical code about 30% slower, but at least it does not suffer from the large pauses that you see in multi-generational GC systems like C#). Rust, BTW, does not use GC, having an even better system that allows it to track and free used memory (or anything) automatically.
  • OO One of the best things about Go is its support for inheritance - there is none. I have spent decades trying to remember all the intricacies of C++ inheritance (and still forget things). Go is simple but has all you need in interfaces and mixins for most modern design patterns. There are some inheritance-based design patterns, such as the template pattern (see Template Method Pattern) which you would not implement in Go but in my opinion these are not good design patterns anyway.
  • Concurrency Many forms of concurrent programming are greatly simplified with the use of go-routines and channels, as I mentioned above.
  • Closures Some narrow-minded people claim that Go is not a modern language because it does not support any modern features like OO, generics and exceptions. This claim is discredited by its support for closures - something that did not even make it into C++ (as lambdas) until 2011. Though not as powerful (ie complicated) as lambdas in C++ they are simple and adequate for use with modern design patterns.
  • Interfaces Interfaces in Go are simpler and more flexible than other languages like Java and C# or the abstract base type of C++, since a type does not need to explicitly state that it implements an interface. People have mentioned complications with this system but in reality it works fine.
  • Information Hiding Go has a very simple system of denoting that a value is visible outside a package. If the identifier starts with a capital letter it is visible (called public in C++, C# etc), otherwise it is only usable inside the package (like internal in C#). Once again this is simple and effective.  I have at times found this cumbersome when I want to hide parts of a package from other parts but I think a refinement that avoids this problem (and may be a better design in general) is to have small "internal" packages.
  • Unit Tests If you have read my blog you know that I love Unit Tests (see my posts from the end of 2013 and the start of 2014 such as this). I have tried different C# and C++ Unit Test frameworks and they can be tedious to understand, set-up and start using. In contrast, the unit test framework that comes with Go and is very easy to use. Note that the name "automated package tests" is preferred (I'm not fond of the term unit test either but it seems to be the term commonly used).
  • Code Coverage A very good thing to do is run code coverage tests on your Unit Tests to ensure that all or most of the code is tested. (Note that even 100% code coverage does not mean you have no bugs but it is a good indicator of how thorough your tests are.)  Despite the benefits, I rarely ran code coverage checks until I started using Go simply because it was too hard. Go makes it easy to get simple code coverage statistics and not that much harder to do even more sophisticated analysis.
  • Benchmarks I use benchmarks a lot, for example to check the performance of a function or compare algorithms and have created my own C++ classes for this purpose. Go comes with a simple, flexible, and effective benchmarking system which can even be used for timing concurrent algorithms.
  • Profiling Profiling allows you to find performance bottlenecks in your software.  Go has built-in support for profiling too, though I have not yet needed to try it.
  • Identifiers Finally, though this is more the culture of Go than the language per se, but I really like the emphasis on short, simple (but meaningful) identifiers instead of some of the monstrosities you see in Java and other languages. See Long Identifiers Make Code Unreadable for more info.

Despite its emphasis on simplicity Go does not always succeed. Many features seem to be designed to make things simpler for "beginners" but end up making things more complex for those who know what they are doing. I am all in favor of making things safer but it should not get in the way of competent developers.  Here are a few examples:
  • Side effects Expressions in Go are based on C expressions but (most) side effects have been removed (ie the operators ++, --, =, +=, etc). I guess this is to avoid expressions with undefined behavior that novices often write in C (like a[i] = i++). The consequence is that things that are easily and sensibly expressed in C/C++ cannot be in Go, often requiring use of temporary variables and more lines of code. This makes code more complex and harder to read. [Note that function calls can still cause side effects in Go expressions resulting in undefined behavior - eg, see this.]
  • Operators Similarly, the ternary (?:) and comma operators are not supported (plus maybe others I have not noticed yet). This cuts down the large and confusing precedence table of C, but makes it painful to produce concise and easily scanned code.
  • Map Iteration Order If you iterate over the elements of a map in Go the order of elements is deliberately unpredictable to prevent someone depending on the order. When I first read of this I thought it was an interesting idea, but what idiot would depend on the order of elements from a hash table?!!  I didn't really foresee any problems with it until I came to debug a problem with data from a map. In that circumstance it is an absolute pain to restart a debug session and find your way back to the same point.
  • Unused Variables One of the biggest annoyances is that the Go compiler won't under any circumstances allow the code to build if there are unused variables or unused imports. Now this is great for finished code but is a complete pain in the q*** when you are writing, testing or debugging.  The justification for using errors and not just a warning is (from the Go website) "if it's worth complaining about, it's worth fixing in the code".  I agree entirely that it's worth fixing just NOT RIGHT NOW. Perhaps this problem can be addressed with a good IDE and better debuggers but it needs urgent addressing.  Here are some examples to demonstrate the problem:
    • I accidentally paste some code into the wrong source file and the IDE (Gogland in this case) "kindly" adds a dozen imports at the top of the file. After I delete accident, the code no longer builds and I have to manually go and delete the bogus imports.
    • I add an import I know I will need and save the file and the IDE (VSCode in this case) "kindly" deletes the unused imports for me - annoying.  Later on when I use the imported function the IDE can't seem to determine how to re-add the import and I have try to remember where it was and add it again manually.
    • I declare a variable and the IDE draws a red squiggle under it to indicate an error. So I click on it to find it's just trying to tell me it is unused. Of course, it's unused I just declared it!
    • I want to see the value of an expression while testing so I assign to a temp variable so I can inspect it in the debugger but then the compiler won't even build the code.
  • Shadowing A source of bugs (in C/C++, Pascal/Delphi, Java, Python, Go and other languages that allow it) is shadowing, where an identifier in an inner scope hides the same name in an outer scope. For example, you might add some code with a new variable which changes the behavior of code at the same level which uses an outer variable of the same name.  In decades of programming in the above languages I have encountered bugs caused by this rarely but Go seems to make it much more likely because of the special if statement and how easy it is to use ":=" instead of "=". Go would be safer if it disallowed shadowing, like in C#, or the compiler could at least warn about it (as many C compilers do).
  • Assertions One of the first things I discovered about Go is that it doesn't have assertions.  (There is even a dubious explanation of this in the official Go FAQ.) I love assertions as they have saved me (literally) years of debugging time but I admit with the advent of exceptions and unit tests they have less use. Luckily, Go actually does have them under the name of panic.
    • - C: assert(a > 0);   // meaningful explanation
    • - C#: Debug.Assert(a > 0, "Meaningful explanation");
    • - Go: if a <= 0 { panic("meaningful explanation") }
  • Exceptions Another thing that there has been a lot of complaint about is Go's lack of exceptions. Admittedly, there are many complexities caused by exceptions (such as very subtle undefined behaviors in C++) but I think it is more a reaction against the rampant misuse of exceptions in much Java code (either that or because modern exception handling was essentially a C++ invention and we don't want anything from C++ in Go :). But again we discover that Go does have exceptions but uses the keywords panic and recover, instead of throw and catch.
  • Error Handling So Go does have exceptions (ie panic/recover) but according to the Go ethos (ie, autocratic pronouncement) this mechanism is only supposed to be used for handling software failures (ie, bugs) not errors. The problem with this is that the distinction between a bug and an error is not always straightforward (eg, see Error Handling vs Defensive Programming in my Defensive Programming post); moreover the Go standard library itself often uses panic in situations that are clearly errors, not bugs. Go does have a few tricks (like defer, multiple-return values, the error type, etc) that make error-handling a bit easier than in C, but the simple fact is that in many situations (and without using panic) error-handling in Go can be a mass of complex, repetitive code. (Of course, Rob Pike and others deny this and demonstrate approaches that are unconvincing, being either just as complex or not universally applicable.)
  • Reference Types Go has pointers but it also has reference types (slices, maps, interfaces, chans, and functions) and the way reference types work is complex. For example a nil slice is treated exactly the same as an empty slice (except when you compare the slice to nil, of course) - and these sorts "split personality" behaviors lead to confusion (like arrays and pointers in C). You can also treat nil maps the same as empty maps except that you can't assign to an element of a nil map.
  • Value/Pointer Receivers The rules about when receivers are converted is confusing. Moreover there seem to be contradictory conventions: (1) use a value receiver for "const" methods and a pointer receiver for methods that modify the receiver (in lieu of "const" methods - see Not C++ point 5) and (2) use a pointer for large types (such as a large struct or an array).
  • Implicit Typing Implicit typing is achieved very simply in Go by using := instead of = for the first use of a variable. (Implicit typing has become very popular - int recent years it has been added to C# [var], C++ [auto], Rust [let] etc.). However, my experience is that I am continually adding/removing explicit declarations, converting between = and := and moving statements into or out of the initialization part of if statements.  This (along with shadowing mentioned above) makes refactoring code tedious and error-prone.
  • Memory Allocation Performance One thing that makes me a little uncomfortable is not knowing where the memory for a variable is coming from. In other languages you know if memory is being allocated from the stack or the heap; but in Go you just have to trust the compiler. I must admit that I have not yet encountered any performance problems but I can't shake the nagging feeling that I (or someone else) may make some innocuous code change and suddenly a lot more memory allocations need to be done from the heap. (My benchmarks have shown that this could slow them by more than 20 times!!)
  • Unit Tests Tests are so easy to write but there is one fatal flaw - tests are part of the package. Anyone with any experience of unit testing knows that tests should only test through the public interface (ie Go automated tests should not be part of the package) otherwise test maintenance becomes far too burdensome (see White Box Testing).
  • Formatting Having programmed in C and syntactically similar languages for almost 4 decades I have encountered a lot of different code formatting and debates on the merits thereof. Personally, I have always strictly conformed to K&R styling rules (even including the slight variations with the release of the 2nd edition of the book) with one important exception - I always place an opening brace on a line by itself. I started doing this in C in the mid-1980's and have been doing it ever since (in C/C++/C# etc). It makes the code easier to scan and I believe it has avoided numerous bugs and build problems by doing this.


I started writing this post many months ago and it keeps changing as I learn more about Go. I have now been using Go for almost six months. I have really found that Go makes life so much easier than any other language I have used, in many many areas. On occasion I yearn for an STL container or algorithm but generally you can do a lot of useful stuff in Go.

That said, there are a few things that I really don't like. Possibly the main one is the condescending attitude of the creators of the language. (I have also detected this to different extents in Smalltalk, Pascal, and Java.) In fact one of the things that I believe turned programmers away in droves from Pascal and towards C in the 1980's (me included) was treating programmers like idiots. Note that I am all in favor of making languages safer, as everyone makes mistakes, but not if it gets in the way of doing things properly.

I guess a good example of this is the fact that it is mandated exactly how code should be formatted. If you get the formatting wrong the code won't even compile. To be honest, I actually like the formatting rules, except for one biggy - that a left brace cannot be on a line by itself, but must be a the end of the preceding line. This convention (from K&R) is an anachronism from a time of paper terminals. In my experience it makes code hard to read and leads to bugs. (In fact I seem to recall Brian Kernighan stating in an interview that the only reason they chose this convention was to keep down printing costs in the original edition of The C Programming Language.)

On a practical note, Go does a good job of avoiding many errors that occur in C. However, in one area, it greatly magnifies the problem - Go makes it extremely easy to create bugs by accidentally shadowing a variable. (In fact just last Friday I discovered another bug of my own due to this.) Something urgently needs to be done about this.

Finally, I just realized that I was going to explain how Go error-handling could be improved, without resorting to exception-handling. Writing error-handling code in Go, like C, is tedious - the sort of job a computer should do. I have a proposal to relieve the tedium but I've rambled on long enough for now so I will have to leave you in suspense until next time.

Next Month: A Proposal for Better Go Error-Handling