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0: Hello world

Before we start writing web servers let's analyze a simple Go program.

package main

import    "fmt"

func         main() {
	fmt.Println("hello, world!")        }

You should be able to understand every line of this program. If you do not it's probably time to check out the Go tour.

Running your code

At this point you can paste the code above into a file named main.go. This file should be anywhere in your $GOPATH. I will assume it is inside of a folder with path $GOPATH/src/hello/main.go.

You can now run the code in a couple of ways. From the directory containing main.go run:

  • go run main.go compiles and runs only main.go.

  • go install compiles the code in the current directory and generates a binary named hello in $GOPATH/bin.

Formatting your code: gofmt

If you're used to seeing some Go code you might have noticed that this code is not formatted in a standard way.

Try running gofmt main.go and you'll see what the output should look like. You can run gofmt -d main.go to see how the file differs from the formatted version. And finally you can run gofmt -w main.go to simply rewrite the file with its formatted version.

Managing import statements: goimports

The import statements at the beginning of the program are needed for the compiler to know what packages you use. But this doesn't mean you need to write them yourself!

Try deleting the line import "fmt" from main.go and run it, you should see an error:

$ go run main.go
# command-line-arguments
./main.go:5: undefined: fmt in fmt.Println

You can fix this error by manually adding the missing import statements or using goimports.

If you don't have goimports installed in your machine you can easily install it by running:

$ go get golang.org/x/tools/cmd/goimports

This will install the goimports binary in $GOAPTH/bin. It is basically the equivalent to fetching the code from GitHub and then running go install.

You can now run goimports as a replacement of gofmt. goimports formats your code and fixes your imported package list adding missing ones and removing those unused.

Similarly to gofmt you can run:

  • goimports main.go to see what the fixed file would look like.
  • goimports -d main.go to see the difference between the current and fixed versions.
  • goimports -w main.go to rewrite the file with its fixed version.

Making your life easier

gofmt and goimports are just two of the tools that you might use to make your life easier. To have those and more invoked everytime you save your file you should consider adding a plugin to your favorite editor. I personally love vim with vim-go and I'm also using VS Code with its Go plugin. But there's many more editors with Go support, you can find them here.

Congratulations!

You're done with section ... zero. Well, we need to start somewhere! But hey, at least now you're ready to tackle section 1.