10.5 Blank Imports

It is an error to import a package into a file but not refer to the name it defines within that file. However, on occasion we must import a package merely for the side effects of doing so: evaluation of the initializer expressions of its package-level variables and execution of its init functions (§2.6.2). To suppress the “unused import” error we would otherwise encounter, we must use a renaming import in which the alternative name is _, the blank identifier. As usual, the blank identifier can never be referenced.

import _ "image/png" // register PNG decoder

This is known as a blank import. It is most often used to implement a compile-time mechanism whereby the main program can enable optional ...

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