MultipartForm

import std.file;
import std.path;
globalLogLevel(LogLevel.info);
info("Check POST files");
/// preapare files
auto tmpd = tempDir();
auto tmpfname1 = tmpd ~ dirSeparator ~ "request_test1.txt";
auto f = File(tmpfname1, "wb");
f.rawWrite("file1 content\n");
f.close();
auto tmpfname2 = tmpd ~ dirSeparator ~ "request_test2.txt";
f = File(tmpfname2, "wb");
f.rawWrite("file2 content\n");
f.close();
///
/// files ready, send them.
/// 
File f1 = File(tmpfname1, "rb");
File f2 = File(tmpfname2, "rb");
scope(exit) {
    f1.close();
    f2.close();
}
MultipartForm form = MultipartForm().
    add(formData("Field1", cast(ubyte[])"form field from memory")).
    add(formData("Field2", cast(ubyte[])"file field from memory", ["filename":"data2"])).
    add(formData("File1", f1, ["filename":"file1", "Content-Type": "application/octet-stream"])).
    add(formData("File2", f2, ["filename":"file2", "Content-Type": "application/octet-stream"]));
auto rq = HTTPRequest();
auto rs = rq.post("http://httpbin.org/post", form);