What does Enable Go modules integration do in Intellij IDE

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Not having previous knowledge about creating a project from zero within terminal, I've created a folder, cd into of it then run go mod init my_project_name which created a go.mod file for me, then I've created main.go file which built just ok.

Then I created a folder and add a go file inside with package name (being same with directory) and create a struct inside of it. Next I tried to import that package in main package but when I try to build on terminal it gave me this error

go: cannot determine module path for source directory /Users/berkcan/workspace/go/my_project_name (outside GOPATH, module path must be specified)

After googling and not being able to find a solution to my problem, I've imported project to beloved Intellij IDE and I enabled Go modules integration then everything worked flawlessly. First I thought IDE doing some magic inside while building project but even when I try go build command in terminal, it built. But I cant see difference in project structure or a new line in go.mod file.

So what happened, what did Intellij IDE did when I ticked go module integration box and what I can do enable it on terminal without Intellij IDE ?

here is the photo of option in IDE when ticked

1 Answers

IntelliJ IDEA plus Go plugin or GoLand under the hood has two modes to get the information about your packages (simplified):

  • GOPATH. IDEA scans your $GOPATH directory to build internal indexes of your packages and provides code completion, resolving, etc.
  • Go Modules. IDEA executes go list -m -json to resolve your dependencies and scans your $GOPATH/pkg/mod directory (default value of GOMODCACHE) for the packages. If they don't exist, IDEA executes go mod download. After these operations, the IDE provides all built-in features like code completion, navigation and so on.

Both modes don't change your Go or environment variables as well as behavior in the terminal. When you check Enable Go Modules integration option in the settings, the IDE just switches the mode from scan $GOPATH to execute go list and resolve your dependencies from the Go Modules cache.

To summarize, IntelliJ IDEA doesn't do any magic. I suppose it relates to your custom Go environment variables inside the terminal, especially GO111MODULE and if you didn't pass these variables to the GUI apps (e.g. you have specified it in .zshrc file and run the IDE via Desktop entry instead of the terminal), IntelliJ IDEA doesn't inherit them. You can compare go env output inside your local terminal and built-in inside the IDE (View | Tool Windows | Terminal) and find differences.

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