Spawn multiple gost processes in a single command with --

[caribpa]

Hi!

This PR is basically #64 but using processes instead of goroutines as preferred by the gost author: #64 (comment)

The code changes are minimal and don't require adapting any of the go-gost libraries! Adding only two functions is all that it takes: https://go.dev/play/p/vJRKMjSrPR3

In a nutshell, this is what this PR allows you to do:

# Server
gost -L sshd://:2222

# Client
gost -L socks5://127.0.0.1:1111 -- -L rtcp://127.0.0.1:3333/127.0.0.1:1111 -F sshd://<server-ip>:2222

# Test from Server
curl -s -L -x socks5://127.0.0.1:3333 https://example.com

instead of having to manually launch separate processes:

# Server
gost -L sshd://:2222

# Client - Terminal/Process 1
gost -L rtcp://127.0.0.1:3333/127.0.0.1:1111 -F sshd://<server-ip>:2222

# Client - Terminal/Process 2
gost -L socks5://127.0.0.1:1111

# Test from Server
curl -s -L -x socks5://127.0.0.1:3333 https://example.com

If merged, I will also port these changes to gost v2 as the PR ginuerzh/gost#713 was implemented using goroutines 😀