Thanks for you help.
I deduce the timeout issue can be image as a network problem. And the go get command is just clone the repository and go install is automatically. So I prefer to achieve my goal by using go install temporarily.
The main.go of github.com/ramya-rao-a/go-outline just has a simple usage of import to get the builduitl. So I still think the error of go install is my fault.
I also had a try on go get to the repository and it might not work well:
$ go get -v -u github.com/ramya-rao-a/go-outline
github.com/ramya-rao-a/go-outline (download)
Fetching https://golang.org/x/tools/go/buildutil?go-get=1
https fetch failed: Get https://golang.org/x/tools/go/buildutil?go-get=1: dial tcp 216.239.37.1:443: i/o timeout
package golang.org/x/tools/go/buildutil: unrecognized import path "golang.org/x/tools/go/buildutil" (https fetch: Get https://golang.org/x/tools/go/buildutil?go-get=1: dial tcp 216.239.37.1:443: i/o timeout)
So maybe anything else I can try to solve the wrong path of my go install? Or maybe it is a misunderstand of it?