How to build grafana v7 from source?

I try to build grafana v7 from source. But it says no Go source files.

(base) ➜  go go get github.com/grafana/grafana
go: downloading github.com/grafana/grafana v1.9.1
go: downloading github.com/grafana/grafana v6.1.6+incompatible
go: github.com/grafana/grafana upgrade => v6.1.6+incompatible
go get github.com/grafana/grafana: no Go source files

Thanks a lot!

I update the go version to 1.14 but still not work.

(base) ➜  ~ go version
go version go1.14.6 darwin/amd64
(base) ➜  go go get github.com/grafana/grafana
go: github.com/grafana/grafana upgrade => v6.1.6+incompatible
go get github.com/grafana/grafana: no Go source files