废话不多说，直接上code

unix server

package main

import (
   "bufio"
   "fmt"
   "net"
   "time"
)

func main() {
   var unixAddr *net.UnixAddr

   unixAddr, err := net.ResolveUnixAddr("unix", "/tmp/usk.sock")
   if err != nil {
       fmt.Println("resolve unix addr fail: " + err)
   }

   unixListener, err := net.ListenUnix("unix", unixAddr)
   if err != nil {
       fmt.Println("listen unix addr fail: " + err)
   }

   defer unixListener.Close()

   for {
       unixConn, err := unixListener.AcceptUnix()
       if err != nil {
           continue
       }

       fmt.Println("A client connected : " + unixConn.RemoteAddr().String())
       go unixPipe(unixConn)
   }

}

func unixPipe(conn *net.UnixConn) {
   ipStr := conn.RemoteAddr().String()
   defer func() {
       fmt.Println("disconnected :" + ipStr)
       conn.Close()
   }()
   reader := bufio.NewReader(conn)

   for {
       message, err := reader.ReadString('\n')
       if err != nil {
           return
       }

       fmt.Println(string(message))
       // lua cosoket need '\n'
       msg := time.Now().String() + "\n"
       b := []byte(msg)
       conn.Write(b)
   }
}

注意： '\n' lua socket

nginx lua client

location /t/tcp {
        resolver 8.8.8.8;

        content_by_lua_block {
              local sock = ngx.socket.tcp()
              local ok, err = sock:connect("www.baidu.com", 80)
              if not ok then
                      ngx.say("failed to connect to baidu: ", err)
                      return
              end
              ngx.say("successfully connected to baidu!")
              sock:close()
        }
  }


  location /t/unix {
        resolver 8.8.8.8;

        content_by_lua_block {
                local sock = ngx.socket.tcp()
                sock:settimeout(300)  -- 0.3 second timeout
      local ok, err = sock:connect("unix:/tmp/usk.sock")
      if not ok then
            ngx.say("failed to connect to unix: ", err)
        return
      end
      ngx.say("successfully connected to unix!")

      local bytes, err = sock:send("I am nginx\n")
        if not bytes then
            ngx.say("failed to send query: ", err)
                return
      end

        local chunk,err = sock:receive()
      if not chunk then
        ngx.say("failed to receive a chunk: ", err)
        return
      end
      ngx.say("content: ", chunk)
      sock:close()
        }
  }

测试命令

➜  /tmp curl 127.0.0.1:8080/t/tcp
successfully connected to baidu!

➜  /tmp curl 127.0.0.1:8080/t/unix
successfully connected to unix!
content: 2020-10-09 03:06:07.196395662 +0000 UTC m=+9.032989967