docs: changed from 'go install' to 'go get' in contributing.md
'go install' is not really the correct command. It does not add the
package to the go.mod file when a specific version is used. The correct
command is 'go get'. See here:
@@ -64,10 +64,10 @@ To add or update a new dependency, use the `go get` command:
```bash
# Pick the latest tagged release.
-go install example.com/some/module/pkg@latest
+go get example.com/some/module/pkg@latest
# Pick a specific version.
-go install example.com/some/module/pkg@vX.Y.Z
+go get example.com/some/module/pkg@vX.Y.Z
```
Tidy up the `go.mod` and `go.sum` files:
