The gopherjs install command examines the contents of a restricted set of files in each directory. It identifies which files to examine based on the extension of the file name. These extensions are:

.go
	Go source files.
.inc.js
	JavaScript source files.
	Automatically included when building the package.

Files of each of these types except .inc.js may contain build constraints, but the gopherjs command stops scanning for build constraints at the first item in the file that is not a blank line or //-style line comment.

• https://github.com/gopherjs/gopherjs/issues/111
• https://github.com/gopherjs/gopherjs/commit/51e33b76d50c8d6648dd80c24db26a5a81a02fcf#commitcomment-8401097
• https://github.com/gopherjs/gopherjs/commit/6395e02fee765127866490fef60b226b42105ac6