I just followed the installation guide for golang (ubuntu 16). I extracted the archive at /etc/usr I added env variable in /home/user/.profile I just tested a basic go build on the hello world code.
I get the following error:
The program 'go' is currently not installed. You can install it by typing: sudo apt install golang-go
Why does it ask me to install it (again?)?
The location of the binary go is not in your path. Ubuntu does not find it and suggests to install it. Add this line to your file /etc/profile, or better $HOME/.profile:
export PATH=$PATH:/usr/local/go/bin
This is documented in the docs: https://golang.org/doc/install#install
If you want to try this solution before editing any files, you can just execute the above command and try to execute the go command in the shell.