Emacs Golang User code does not complete the problem

This is a created article in which the information may have evolved or changed.

Phenomenon: Emacs uses company-go to fully complement standard library functions and go get installation library functions, and for self-written code, only the variables and functions under the current package can be completed.

Cause: Company-go backstage is used Gocode, and Gocode complement will not parse the code but parse. A file, so the user code needs to go install each package.

First online to find the answer, test Emacs version 25,26,27, and then read the Company-go code, engage in a few hours, and finally locate the reason, and later found Gocode document actually has the description, just put in the last, ==! Hope to be useful to other students who trample the pits.