The Go compiler indents sometimes filenames. I have attached a
htmlfontified compilation buffer showing this. It also shows that the
parser of the compilation buffer gets confused by this. The
problematic line is:

"    ./config.go:10:5: other declaration of config_file"

Some code thinks the whole line is a file name, because the whole line
is a hyperlink (underlined).

Some other code thinks only the beginning of the line is a file name
(red). But this part also thinks the line number is part of the file
name and marks the column number as line number (purple).

I think it might be ok to ignore leading whitespace, because file
names do not start very often with whitespace.