Module Not Found

Why This Happens

Go modules require all dependencies to be listed in go.mod. If you import a package that is not in go.mod, the compiler cannot find it. Run go get to download the module and add it to your go.mod and go.sum files.

The Problem

// go.mod does not include the dependency
import "github.com/gorilla/mux" // module not found

The Fix

// Run: go get github.com/gorilla/mux
import "github.com/gorilla/mux" // now works

Step-by-Step Fix

1. 1

   Identify the missing module

   Read the error to find the exact module path that cannot be found.

2. 2

   Add the dependency

   Run go get github.com/foo/bar to download and add it to go.mod.

3. 3

   Verify with go mod tidy

   Run go mod tidy to clean up and verify all dependencies are correct.