Exec Wait Strategy
The exec wait strategy will check the exit code of a process to be executed in the container, and allows to set the following conditions:
- the command and arguments to be executed, as an array of strings.
 - a function to match a specific exit code, with the default matching 
0. - the startup timeout to be used in seconds, default is 60 seconds.
 - the poll interval to be used in milliseconds, default is 100 milliseconds.
 
Match an exit code
req := ContainerRequest{
    Image:        "docker.io/nginx:alpine",
    WaitingFor: wait.NewExecStrategy([]string{"git", "version"}).WithExitCodeMatcher(func(exitCode int) bool {
        return exitCode == 10
    }),
}