libevent库
执行./configure 时出现以下错误：
configure: error: openssl is a must but can not be found. You should add the directory containing ‘openssl.pc’ to the PKG_CONFIG_PATH’ environment variable, or set ‘CFLAGS’ and ‘LDFLAGS’ directly for openssl, or use ‘–disable-openssl’ to disable support for openssl encryption
解决方案：
ubuntu 平台 sudo apt install libssl-dev