Code from http://isocpp.org/files/papers/n4045.pdf

n4045 example.cpp

string                                     // task<string>
read(string file, string suffix,           // read(string file, string suffix)
     yield_context yield) {                //      __async {
    istream fi = open(file, yield);        //     istream fi = __await open(file);
    string ret, chunk;
    while((chunk = fi.read(yield)).size()) //     while((chunk = __await fi.read()).size())
        ret += chunk + suffix;
    return ret;
}