extension/tools/release: fix errors in checkPackageJSON

The version in package.json and the version in tag should match.
The check was reversed.

And fix the error message about the missing environment variable.

Change-Id: I945a9a5f678d9bf9762a2e754db5fe3f54c433c7
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/606777
Reviewed-by: Hongxiang Jiang <[email protected]>
Commit-Queue: Hyang-Ah Hana Kim <[email protected]>
kokoro-CI: kokoro <[email protected]>

Author: hyangah

extension/tools/release/release.go

@@ -275,7 +275,7 @@ func requireTools(tools ...string) {
 func requireEnv(name string) string {
 	v := os.Getenv(name)
 	if v == "" {
-		fatalf("required environment variable %q not set", v)
+		fatalf("required environment variable %q not set", name)
 	}
 	return v
 }
@@ -354,7 +354,7 @@ func checkPackageJSON(tagName string, isPrerelease bool) {
 	}
 	// Check only major.minor for prerelease.
 	major, minor, _, _ := parseVersionTagName(tagName)
-	if want := fmt.Sprintf("%d.%d.", major, minor); strings.HasPrefix(versionInPackageJSON, want) {
+	if want := fmt.Sprintf("%d.%d.", major, minor); !strings.HasPrefix(versionInPackageJSON, want) {
 		fatalf("package.json version %q does not match wanted string %q", versionInPackageJSON, want)
 	}
 }