mplayer fail to get stdin stream from golang

I want to write a simple command line m3u8 player for Linux. (Let me know if there already one.)

There are several ts file urls in m3u8 file. m3u8 file is dynamically changed from network. Usually, one ts file has only a few seconds. So I need to download m3u8 file and ts files in it again and again. Then I use mplayer to play the stream continuesly. I suppose this is a network radio.

Here is what I have done:

First, I lauch mplayer process and get the stdin:

mplayer_cmd := exec.Command("sh", "-c", "mplayer -msglevel all=9 -cache 80 -")
mplayer_writer, mplayer_err := mplayer_cmd.StdinPipe()

Then, I get m3u8 file and ts urls in it and wget content of ts file and write it to stdin of mplayer. And I do this step again and again:

out, err = exec.Command("sh", "-c", "wget " + m3u8_url + " -qO - | grep '.ts'").Output()
...
out, err = exec.Command("sh", "-c", "wget " + ts_url + " -qO -").Output()
...
n, err = mplayer_writer.Write(out)
fmt.Println("wrote ", n)

No sound come out from mplayer. Comparing to a successful running from command line, there is such related error messsage:

Cache empty, consider increasing -cache and/or -cache-min. [performance issue]

A suspect info is that - mplayer fork a child process when lauch. Will stdin/stdout pipe broken in this situation?

 | |       \-+- 03027 hgneng mplayer -msglevel all=9 -cache 80 -
 | |         \--- 03033 hgneng mplayer -msglevel all=9 -cache 80 -

Sorry, it's my fault. I get the stdout pipe of mplayer somewhere for debug. However, the code hangs there because there is no output. I found this with godebug.