Linker error: ld: library not found for -lssl [duplicate] - mysql

Question

I installed crystal with homebrew brew install crystal-lang. I was able to compile and run a "Hello World!" program, but when I try to compile the example http server (with one slight modification) I get an error.
HTTP server:
require "http/server"
port = 3000
server = HTTP::Server.new(port) do |context|
context.response.content_type = "text/plain"
context.response.print "Hello world! The time is #{Time.now}"
end
puts "listening on http://localhost:" + port.to_s
puts "listening on http://localhost:#{port}"
server.listen
Error:
$ crystal server.cr ~/sw/crystal/Lied-Today
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error: execution of command failed with code: 1: `cc -o "/Users/Matt/.cache/crystal/crystal-run-server.tmp" "${#}" -rdynamic -lz `command -v pkg-config > /dev/null && pkg-config --libs libssl || printf %s '-lssl -lcrypto'` `command -v pkg-config > /dev/null && pkg-config --libs libcrypto || printf %s '-lcrypto'` -lpcre -lgc -lpthread /usr/local/Cellar/crystal-lang/0.21.1_1/src/ext/libcrystal.a -levent -liconv -ldl -L/usr/lib -L/usr/local/lib`
I've tried the following:
Adding export LIBRARY_PATH="$LIBRARY_PATH:/usr/local/lib" to ~/.zshrc.
and
$ xcode-select --install
$ xcode-select --switch /Library/Developer/CommandLineTools

Answer 1

I had to add LIBRARY_PATH to fix this.
export LIBRARY_PATH=$LIBRARY_PATH:/usr/local/opt/openssl/lib/

Answer 2

I needed to let Xcode finish installing, before running the second xcode-select command.

Answer 3

Just include the Lib
brew install openssl
echo 'export LIBRARY_PATH=$LIBRARY_PATH:/usr/local/opt/openssl/lib/' >> ~/.zshrc
source ~/.zshrc

Answer 4

Providing pkgconfig path for openssl library fixed the problem for me:
PKG_CONFIG_PATH="/usr/local/opt/openssl/lib/pkgconfig" crystal <command>

Answer 5

Adding the package config Juan mentioned worked for me, here are commands to add it so you don't need to specify every time:
echo 'export PATH="/usr/local/opt/llvm#8/bin:$PATH"' >> ~/.bash_profile
source ~/.bash_profile

Answer 6

As of MacOS Monterey, Matias' solution works and it's also in the official documentation now.
brew install openssl
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/opt/openssl/lib/pkgconfig