Moved module env var check to modcmd from modinit

src/cmd/go/internal/modcmd/init.go

@@ -35,6 +35,9 @@ func runInit(cmd *base.Command, args []string) {
 	if len(args) == 1 {
 		modload.CmdModModule = args[0]
 	}
+	if os.Getenv("GO111MODULE") == "off" {
+		base.Fatalf("go mod init: modules disabled by GO111MODULE=off; see 'go help modules'")
+	}
 	if _, err := os.Stat("go.mod"); err == nil {
 		base.Fatalf("go mod init: go.mod already exists")
 	}

src/cmd/go/internal/modload/init.go

@@ -99,7 +99,8 @@ func Init() {
 	case "on", "":
 		mustUseModules = true
 	case "off":
-		die()
+		mustUseModules = false
+		return
 	}
 
 	// Disable any prompting for passwords by Git.