Environment Variables

GOPATH vs GOROOT

• GOROOT is a variable that defines where your Go SDK (installation) is located. You do not need to change this variable, unless you plan to use different Go versions. To find the GOPATH location, type go env:
  • Default Linux/macOS location: /usr/local/go/
  • Default Windows location: %PROGRAMFILES%/go
• GOPATH is a variable that defines the root of your Workspace, where all Go code is organized to store your codebase. To find the GOPATH location, type go env:
  • Default Linux/macOS location: /home/user/go/ or ~/go
  • Default Windows location: %USERPROFILE%/go

GOPATH Subdirectories

1. ~/go/src/ - source code location
2. ~/go/pkg/ - shared libraries location
3. ~/go/bin/ - compiled code location

Package Management

History of Go Modules

• In version 1.13, the authors of Go added a new way of managing the libraries of a Go project to depend on Go modules. With the introduction of Go modules, it became possible for Go projects to be located anywhere on the filesystem, not just a specific directory defined by Go. Go modules were added in response to a growing need to make it easier for developers to maintain various versions of their dependencies, as well as add more flexibility in the way developers organize their projects on their computer.
  • At first there was no *.mod file because Go wanted to enforce one centralized location for managing packages in the /pkg directory that the GOPATH looks for. However, people started complaining that in their /src path, they can’t separate different versions or have isolated environments (even though renaming folders could fix this easily).
  • Thus was born the “Module”, which is basically like a secondary GOPATH that automagically switches on top of the current gopath. The gopath still exists in order to be backwards compatible. Each time you go to a module folder with a *.mod file, you can type go env in your terminal and see the gomod environment variable magically change to the current folder where the module is and the gopath will remain the same.
  • Since GOPATH/pkg is where Go stores pre-compiled object files to speed up subsequent compiling of programs, they had no choice but to create a second subfolder for isolation. And the /mod folder functions the same way as /pkg, but just separated from the rest to avoid version conflicts but still benefit from the fast compilation times within a higher hierarchy. It is by design to keep compilation centralized, yet decoupled for modules.

A module has many projects. Modules are isolated workspaces, decoupled from the gopath. This is useful if many code-bases exist on different systems.

Creating a Module

Initializing a Folder as a Module

1. Go to inside the folder where you want the module to be and type **go mod init <module name>. This will create a go.mod file in the folder. The module name does not need to match the folder name
2. Inside go.mod, the file should look like this:

module mymodule
go 1.16