Error when running a .exe Go program if I add a line break in the import

Most probably, when you execute go run run_go.cmd Go compiles your program into a hidden nested temporary directory AppData\Local\Temp and executes it dynamically, so Windows Defender evaluates temporary compiler cache executions with different heuristic rules than it does for freshly generated .exe in your local project folder. Also, minor difference changes the final hash and file structure of .exe, - in one layout it unintentionally matches a known malicious signature heuristic, - in another layout it does not.