protoc-gen-go: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/protoc-gen-go - from package: golang-googlecode-goprotobuf

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/protoc-gen-go - from package: golang-goprotobuf-dev

You may install the required package with command apt-get install {package}

Error in other languages:
protoc-gen-go: bevel nie gevind nie
protoc-gen-go: comandă negăsită
protoc-gen-go: comando não encontrado
protoc-gen-go: commande introuvable
protoc-gen-go: command not found
protoc-gen-go: käsku ei ole
protoc-gen-go: không tìm thấy lệnh
protoc-gen-go: komanda nerasta
protoc-gen-go: Kommando nicht gefunden.
protoc-gen-go: kommandot finns inte
protoc-gen-go: komut yok
protoc-gen-go: nie znaleziono polecenia
protoc-gen-go: níor aimsíodh an t-ordú
protoc-gen-go: no se encontró la orden
protoc-gen-go: no s'ha trobat l'ordre
protoc-gen-go: opdracht niet gevonden
protoc-gen-go: parancs nem található
protoc-gen-go: perintah tidak ditemukan
protoc-gen-go: príkaz nenájdený
protoc-gen-go: příkaz nenalezen
protoc-gen-go: команда не найдена
protoc-gen-go: командата не е открита
protoc-gen-go: 命令找不到
protoc-gen-go: コマンドが見つかりません