Mimemagic - Detect mime-types in Go
Import the library
mimemagic.Match(myguess string, startoffile byte) string
The API: myguess is a guess of the mimetype that is checked first before other types are checked. It may also be "". startoffile contains the beginning of the file - e.g. giving it 1024 bytes from the start of the file works fine. * the result is the guessed mimetype or "" if not known.