cmd/govulncheck: delete no-go-sum error

This error is not necessary as the original error message "missing
go.sum entry ..." is clear enough. Otherwise, the current classification
of this error was wrong and would mask other important errors.

Also cleans up other currently unused errors.

Fixes golang/go#57013

Change-Id: If67ea4423b81bf35103c67d10c7e1eb291470fb3
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/456135
Run-TryBot: Zvonimir Pavlinovic <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Julie Qiu <[email protected]>

Author: sayjun0505

cmd/govulncheck/errors.go

@@ -27,21 +27,6 @@ govulncheck with the current Go version.`)
 govulncheck only works Go with modules. Try navigating to your module directory.
 Otherwise, run go mod init to make your project a module.
 
-See https://go.dev/doc/modules/managing-dependencies for more information.`)
-
-	// errNoGoSum indicates that a go.sum file was not found in this module.
-	errNoGoSum = errors.New(`no go.sum file
-
-Your module is missing a go.sum file. Try running go mod tidy.
-
-See https://go.dev/doc/modules/managing-dependencies for more information.`)
-
-	// errNoModVersion indicates that govulncheck cannot access module version information.
-	errNoModVersion = errors.New(`no module version information
-
-This can happen when running govulncheck in GOPATH mode. govulncheck needs module
-versions to correctly identify vulnerabilities.
-
 See https://go.dev/doc/modules/managing-dependencies for more information.`)
 )
 

cmd/govulncheck/main.go

@@ -106,9 +106,6 @@ func doGovulncheck(patterns []string, sourceAnalysis bool) error {
 			if !fileExists(filepath.Join(dir, "go.mod")) {
 				return errNoGoMod
 			}
-			if !fileExists(filepath.Join(dir, "go.sum")) {
-				return errNoGoSum
-			}
 			if isGoVersionMismatchError(err) {
 				return fmt.Errorf("%v\n\n%v", errGoVersionMismatch, err)
 			}