cannot find definition of code in vendor directory

[jiajunhuang]

1. create main.go in gopath

package main

import (
	"go.uber.org/zap"
)

func main() {
	logger, _ := zap.NewProduction()
	defer logger.Sync()

	logger.Info("haha")
}

2. run dep ensure -add "go.uber.org/zap"

3. use vim, open main.go, jump to line 11, under Info of logger.Info, and run :YcmCompleter GoTo,
   got RuntimeError: Can't find a definition.

4. ycmd says: RuntimeError: Command godef -i -f=main.go -json -o=126 failed with code 2 and error "godef: no declaration found for logger.Info".

5. run it in command:

$ godef -i -f=main.go -o=126 < main.go
parseLocalPackage error: no more package files found
godef: no declaration found for logger.Info

ref: ycm-core/YouCompleteMe#2985 (comment)