fix: add pkg-config (#125)

Dockerfile

@@ -53,7 +53,7 @@ RUN mkdir -p "$GOPATH/src" "$GOPATH/bin" && chmod -R 777 "$GOPATH"
 RUN curl -sL https://deb.nodesource.com/setup_15.x | bash - && apt-get install -y nodejs
 # the following is a workaround for openjdk-11-jre-headless erroring due to not having a man path in slim-debian
 RUN apt-get update -y
-RUN apt-get install -y --no-install-recommends python3 python3-dev python3-pip ruby jq gnupg git gettext libffi6 libffi-dev libssl-dev php composer php-curl php7.3-tokenizer php-dom php-xml php-simplexml php-xmlwriter maven
+RUN apt-get install -y --no-install-recommends python3 python3-dev python3-pip ruby jq gnupg git gettext libffi6 libffi-dev libssl-dev php composer php-curl php7.3-tokenizer php-dom php-xml php-simplexml php-xmlwriter maven pkg-config
 # RUN apk add -U --no-cache ca-certificates bash nodejs npm python3 python3-dev py-pip ruby jq build-base gnupg git openssh curl gettext libffi libffi-dev openssl-dev php composer php-curl php7-tokenizer wget php-dom php-xml php-simplexml php-xmlwriter maven
 
 # https://stackoverflow.com/questions/35736598/cannot-pip-install-cryptography-in-docker-alpine-linux-3-3-with-openssl-1-0-2g