[FEATURE] Write the documents for 31-goroutine

[yunwei37]

Is your feature request related to a problem? Please describe.

The example for https://github.com/eunomia-bpf/bpf-developer-tutorial/tree/main/src/31-goroutine is working. We need to write a tutorial for it.

Describe the solution you'd like

Write a README.md and README_en.md in https://github.com/eunomia-bpf/bpf-developer-tutorial/tree/main/src/31-goroutine, make it a tutorial.