MatchFile returns false if the name contains a $GOOS or $GOARCH suffix which does not match the current system.

ReadComments is like ioutil.ReadAll, except that it only reads the leading block of comments in the file.

ReadImports is like ioutil.ReadAll, except that it expects a Go file as input and stops reading the input once the imports have completed.

ShouldBuild reports whether it is okay to use this file, The rule is that in the file's leading run of // comments and blank lines, which must be followed by a blank line (to avoid including a Go package clause doc comment), lines beginning with '// +build' are taken as build directives.