记录下在 Mac 下编译 linux 可执行文件需要做的事情：
# Install the toolchain to build Linux x86_64 binaries
$ rustup target add x86_64-unknown-linux-gnu
# we need a program that links our compiled objects together
$ brew tap SergioBenitez/osxct
$ brew install x86_64-unknown-linux-gnu
# we need to tell Rust about the linker
# The official way to do this is to add a new file named `.cargo/config` in the root of your
# project and set its content to something similar:
[target.x86_64-unknown-linux-gnu]
linker = "x86_64-linux-gnu-gcc"
# [optional] if you have any C code compiled by a Rust build script, you also have to
# set environment variables like `TARGET_CC` to get it working:
$ export TARGET_CC=x86_64-linux-gnu-gcc
如果你的依赖包（比如reqwest）有用到openssl，编译的时候还是会报错。。最简单的解决办法是不依赖 openssl！
可以在Cargo.toml里这样设置来让 reqwest 使用 rustls 而不是 openssl：
reqwest = { version = "0.11", features = ["rustls-tls"], default-features = false }
- A "rustup target" Example: Using a Mac to cross-compile Linux binaries
- Cross Compile Rust from Mac to Linux
没有白费功夫，性能提升明显！
在 concurrency 设置为 5 的时候，发起请求的 qps 约为 python 版本（使用了multiprocessing）的 4 倍；
在 concurrency 设置为 10 的时候，发起请求的 qps 约为 python 版本（使用了multiprocessing）的 8 倍；