Function lua_yieldk 

pub fn lua_yieldk(
    state: &mut LuaState,
    nresults: i32,
    ctx: isize,
    k: Option<LuaKFunction>,
) -> Result<i32, LuaError>

Yields the current coroutine, saving the continuation function k and context ctx for resumption.

C: LUA_API int lua_yieldk(lua_State *L, int nresults, lua_KContext ctx, lua_KFunction k)