diff --git a/.gitignore b/.gitignore
index 87bb3e3..f729b04 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+docker/Dockerfile
 .vscode
 prom/build/*
 promhttp/build/*
diff --git a/.travis.yml b/.travis.yml
index 4b111d2..f95a088 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,4 +5,12 @@ language: c
 services:
   - docker
 
-script: make
\ No newline at end of file
+script: make
+
+jobs:
+  include:
+    - env: DOCKER_IMAGE=ubuntu:18.04
+    - env: DOCKER_IMAGE=ubuntu:16.04
+    - env: DOCKER_IMAGE=debian:buster
+    - env: DOCKER_IMAGE=debian:stretch
+    - env: DOCKER_IMAGE=debian:jessie
diff --git a/Makefile b/Makefile
index fb2042a..39a5117 100644
--- a/Makefile
+++ b/Makefile
@@ -13,17 +13,13 @@ default: changed_files
 	@echo -e "\033[1;32mNothing to build\033[0m"
 endif
 
-build_and_test: changed_files docker clean build test package smoke
+build_and_test: changed_files clean build test package smoke
 .PHONY: build_and_test
 
 all: build_and_test docs
 .PHONY: all
 
-docker:
-	pushd docker && make
-.PHONY: docker
-
-clean: docker
+clean:
 	./auto dev -e auto -a clean
 
 build: clean
diff --git a/README.md b/README.md
index 4e00181..099d68b 100644
--- a/README.md
+++ b/README.md
@@ -73,3 +73,9 @@ communication process so please do not be shy. Speak up!
 ## Misc
 
 * Language level: C11
+* Operating Systems:
+  * Ubuntu 18.04
+  * Ubuntu 16.04
+  * Debian Buster
+  * Debian Stretch
+  * Debian Jessie
diff --git a/auto b/auto
index 4aaa6ba..120d4e2 100755
--- a/auto
+++ b/auto
@@ -10,7 +10,8 @@ if [[ "$AUTO_DEBUG" == "1" ]]; then
   export AUTO_DEBUG=1
 fi
 
-PROJECT_ROOT=$(pushd $(dirname $0) > /dev/null; echo $PWD; popd > /dev/null)
+export PROJECT_ROOT=$(pushd $(dirname $0) > /dev/null; echo $PWD; popd > /dev/null)
+export DOCKER_IMAGE
 PROGRAM_NAME="$(basename $0)"
 
 usage(){
diff --git a/autolib/autolib.sh b/autolib/autolib.sh
index 54ff558..4230995 100644
--- a/autolib/autolib.sh
+++ b/autolib/autolib.sh
@@ -4,5 +4,6 @@ lib="$(dirname ${BASH_SOURCE[0]})"
 
 source "${lib}/output.sh"
 source "${lib}/build.sh"
+source "${lib}/docker.sh"
 source "${lib}/env.sh"
-source "${lib}/test.sh"
\ No newline at end of file
+source "${lib}/test.sh"
diff --git a/autolib/cmd/dev b/autolib/cmd/dev
index 012798f..2f5ed13 100755
--- a/autolib/cmd/dev
+++ b/autolib/cmd/dev
@@ -21,6 +21,9 @@ MUST NOT execute this command from an existing docker container.
 -e Execute the following executable
 -a Pass an argument to the executable given by -e. You may specify
    this flag multiple times. The order is preserved.
+-i The docker image to use.
+   Default: ubuntu:18.04
+   Options: ubuntu:18.04, ubuntu:16.04, debian:buster, debian:stretch, debian:jessie
 EOF
 
 usage() {
@@ -43,21 +46,21 @@ EOF
 
 source $(dirname ${BASH_SOURCE[0]})/../autolib.sh
 
+declare DOCKER_IMAGE=${DOCKER_IMAGE:=ubuntu:18.04}
 declare DOCKER_EXEC
 declare -a DOCKER_EXEC_ARGS
 
 run(){
   local r
-  if ! { docker image list | grep -q prometheus-client-c-dev; }; then
-    autolib_output_banner "Building development container"
-    pushd docker > /dev/null || return $?
-      make || {
-        r=$?
-        outlib_output_error "Docker Build Failure"
-        return $r
-      }
-    popd > /dev/null
-  fi
+  autolib_output_banner "Building development container"
+  autolib_write_dockerfile "$DOCKER_IMAGE" || return $?
+  pushd docker > /dev/null || return $?
+    make || {
+      r=$?
+      outlib_output_error "Docker Build Failure"
+      return $r
+    }
+  popd > /dev/null
 
   autolib_output_banner "Entering development environment"
   declare -a args
@@ -75,11 +78,14 @@ run(){
 }
 
 main(){
-  while getopts "he:a:" opt; do
+  while getopts "he:a:i:" opt; do
     case $opt in
       ( h ) {
         usage && exit 0
       } ;;
+      ( i ) {
+        DOCKER_IMAGE="$OPTARG"
+      } ;;
       ( e ) {
         DOCKER_EXEC="$OPTARG"
       } ;;
diff --git a/autolib/docker.sh b/autolib/docker.sh
new file mode 100644
index 0000000..bfef40d
--- /dev/null
+++ b/autolib/docker.sh
@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+
+lib="$(dirname ${BASH_SOURCE[0]})"
+source "${lib}/output.sh"
+
+PROJECT_ROOT=$(pushd "$(dirname ${BASH_SOURCE[0]})/.." > /dev/null; echo $PWD; popd > /dev/null)
+
+autolib_debian_template(){
+  cat <<'EOF'
+FROM __DOCKER_IMAGE__
+
+RUN apt-get update && \
+    apt-get install -y apt-utils && \
+    apt-get install -y curl tar build-essential git pkg-config gdb valgrind gcc libmicrohttpd-dev doxygen graphviz && \
+    curl -sL https://github.com/Kitware/CMake/releases/download/v3.14.5/cmake-3.14.5-Linux-x86_64.tar.gz | tar xzf - -C /opt && \
+    cp /opt/cmake-3.14.5-Linux-x86_64/bin/* /usr/local/bin/ && \
+    cp -R /opt/cmake-3.14.5-Linux-x86_64/share/cmake-3.14 /usr/local/share/ && \
+    curl -sL https://dl.google.com/go/go1.13.1.linux-amd64.tar.gz 2> /dev/null | tar xzf - -C /usr/local && \
+    mkdir -p /gopath/{src,bin} && \
+    printf 'export GOPATH=/gopath\nexport PATH=$PATH:/usr/local/go/bin:/gopath/bin\n' > /root/.bash_profile && \
+    printf '#!/usr/bin/env bash\nsource /root/.bash_profile\nexec /bin/bash $@\n' > /entrypoint && \
+    chmod +x /entrypoint && \
+    GOPATH=/gopath /usr/local/go/bin/go get github.com/prometheus/prom2json && \
+    GOPATH=/gopath /usr/local/go/bin/go install github.com/prometheus/prom2json/cmd/prom2json && \
+    GOPATH=/gopath /usr/local/go/bin/go get github.com/git-chglog/git-chglog && \
+    GOPATH=/gopath /usr/local/go/bin/go install github.com/git-chglog/git-chglog/cmd/git-chglog && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /code
+ENTRYPOINT ["/entrypoint"]
+
+EOF
+}
+
+autolib_write_dockerfile(){
+  local docker_image="$1"
+  local r
+  case "$docker_image" in
+    ( ubuntu:18.04 | ubuntu:16.04 | debian:buster | debian:stretch | debian:jessie ) {
+      autolib_debian_template | sed "s/__DOCKER_IMAGE__/$docker_image/g" > ${PROJECT_ROOT}/docker/Dockerfile || {
+        r=$?
+        autolib_output_error "failed to generate dockerfile"
+        return $r
+      }
+    } ;;
+
+    ( * ) {
+      r=1
+      autolib_output_error "unsupported DOCKER_IMAGE: $docker_image"
+      return $r
+    } ;;
+  esac
+}
\ No newline at end of file
diff --git a/docker/Dockerfile b/docker/Dockerfile
deleted file mode 100644
index 48b0e52..0000000
--- a/docker/Dockerfile
+++ /dev/null
@@ -1,20 +0,0 @@
-FROM ubuntu:18.04
-
-RUN apt-get update && \
-    apt-get install -y apt-utils && \
-    apt-get install -y curl tar build-essential git pkg-config gdb valgrind gcc libmicrohttpd-dev doxygen graphviz && \
-    curl -L https://dl.google.com/go/go1.13.1.linux-amd64.tar.gz 2> /dev/null | tar xzvf - -C /usr/local && \
-    mkdir -p /gopath/{src,bin} && \
-    printf 'export GOPATH=/gopath\nexport PATH=$PATH:/usr/local/go/bin:/gopath/bin\n' > /root/.bash_profile && \
-    printf '#!/usr/bin/env bash\nsource /root/.bash_profile\nexec /bin/bash $@\n' > /entrypoint && \
-    chmod +x /entrypoint && \
-    GOPATH=/gopath /usr/local/go/bin/go get github.com/prometheus/prom2json && \
-    GOPATH=/gopath /usr/local/go/bin/go install github.com/prometheus/prom2json/cmd/prom2json && \
-    GOPATH=/gopath /usr/local/go/bin/go get github.com/git-chglog/git-chglog && \
-    GOPATH=/gopath /usr/local/go/bin/go install github.com/git-chglog/git-chglog/cmd/git-chglog && \
-    curl -L https://github.com/Kitware/CMake/releases/download/v3.15.0-rc1/cmake-3.15.0-rc1.tar.gz | tar xzvf - -C /tmp/ && \
-    cd /tmp/cmake-3.15.0-rc1 && ./bootstrap && make && make install && \
-    rm -rf /var/lib/apt/lists/*
-
-WORKDIR /code
-ENTRYPOINT ["/entrypoint"]
\ No newline at end of file
diff --git a/example/main.c b/example/main.c
index c93e149..d695d12 100644
--- a/example/main.c
+++ b/example/main.c
@@ -74,7 +74,7 @@ int main(int argc, const char **argv) {
   }
 
 
-  struct MHD_Daemon *daemon = promhttp_start_daemon(MHD_USE_INTERNAL_POLLING_THREAD, 8000, NULL, NULL);
+  struct MHD_Daemon *daemon = promhttp_start_daemon(MHD_USE_SELECT_INTERNALLY, 8000, NULL, NULL);
   if (daemon == NULL) {
     return 1;
   }
diff --git a/prom/CMakeLists.txt b/prom/CMakeLists.txt
index dc0c494..aaa8877 100644
--- a/prom/CMakeLists.txt
+++ b/prom/CMakeLists.txt
@@ -1,4 +1,6 @@
 cmake_minimum_required(VERSION 3.14.5)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
 
 execute_process(
     COMMAND cat ${CMAKE_CURRENT_SOURCE_DIR}/../VERSION
diff --git a/prom/src/prom_map.c b/prom/src/prom_map.c
index a36cad7..677c66d 100644
--- a/prom/src/prom_map.c
+++ b/prom/src/prom_map.c
@@ -136,12 +136,6 @@ int prom_map_destroy(prom_map_t *self) {
   prom_free(self->addrs);
   self->addrs = NULL;
 
-  r = pthread_rwlock_unlock(self->rwlock);
-  if (r) {
-    PROM_LOG(PROM_PTHREAD_RWLOCK_UNLOCK_ERROR);
-    ret = r;
-  }
-
   r = pthread_rwlock_destroy(self->rwlock);
   if (r) {
     PROM_LOG(PROM_PTHREAD_RWLOCK_DESTROY_ERROR)
diff --git a/prom/src/prom_metric.c b/prom/src/prom_metric.c
index cbfab34..47d7fdf 100644
--- a/prom/src/prom_metric.c
+++ b/prom/src/prom_metric.c
@@ -119,12 +119,6 @@ int prom_metric_destroy(prom_metric_t *self) {
   self->formatter = NULL;
   if (r) ret = r;
 
-  r = pthread_rwlock_unlock(self->rwlock);
-  if (r) {
-    PROM_LOG(PROM_PTHREAD_RWLOCK_UNLOCK_ERROR);
-    ret = r;
-  }
-
   r = pthread_rwlock_destroy(self->rwlock);
   if (r) {
     PROM_LOG(PROM_PTHREAD_RWLOCK_DESTROY_ERROR);
diff --git a/prom/src/prom_metric_sample_histogram.c b/prom/src/prom_metric_sample_histogram.c
index 4fe6cac..28533b7 100644
--- a/prom/src/prom_metric_sample_histogram.c
+++ b/prom/src/prom_metric_sample_histogram.c
@@ -327,9 +327,6 @@ int prom_metric_sample_histogram_destroy(prom_metric_sample_histogram_t *self) {
   if (r) ret = r;
   self->metric_formatter = NULL;
 
-  r = pthread_rwlock_unlock(self->rwlock);
-  if (r) ret = r;
-
   r = pthread_rwlock_destroy(self->rwlock);
   if (r) ret = r;
 
diff --git a/promhttp/CMakeLists.txt b/promhttp/CMakeLists.txt
index e0451d0..9565c8d 100644
--- a/promhttp/CMakeLists.txt
+++ b/promhttp/CMakeLists.txt
@@ -1,4 +1,6 @@
 cmake_minimum_required(VERSION 3.14.5)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
 
 execute_process(
     COMMAND cat ${CMAKE_CURRENT_SOURCE_DIR}/../VERSION
diff --git a/promtest/CMakeLists.txt b/promtest/CMakeLists.txt
index 32ae3b0..3c6de45 100644
--- a/promtest/CMakeLists.txt
+++ b/promtest/CMakeLists.txt
@@ -1,4 +1,6 @@
 cmake_minimum_required(VERSION 3.14.5)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
 
 execute_process(
     COMMAND cat ${CMAKE_CURRENT_SOURCE_DIR}/../VERSION
diff --git a/promtest/test/promtest_counter.c b/promtest/test/promtest_counter.c
index a2940f7..c57cd56 100644
--- a/promtest/test/promtest_counter.c
+++ b/promtest/test/promtest_counter.c
@@ -105,7 +105,7 @@ int promtest_counter_setup(void) {
   promhttp_set_active_collector_registry(NULL);
 
   // Start the HTTP server
-  promtest_daemon = promhttp_start_daemon(MHD_USE_INTERNAL_POLLING_THREAD, 8000, NULL, NULL);
+  promtest_daemon = promhttp_start_daemon(MHD_USE_SELECT_INTERNALLY, 8000, NULL, NULL);
 
   if (promtest_daemon == NULL) return 1;
   else return 0;
diff --git a/promtest/test/promtest_gauge.c b/promtest/test/promtest_gauge.c
index a8202d2..c33450d 100644
--- a/promtest/test/promtest_gauge.c
+++ b/promtest/test/promtest_gauge.c
@@ -105,7 +105,7 @@ int promtest_gauge_setup(void) {
   promhttp_set_active_collector_registry(NULL);
 
   // Start the HTTP server
-  promtest_daemon = promhttp_start_daemon(MHD_USE_INTERNAL_POLLING_THREAD, 8000, NULL, NULL);
+  promtest_daemon = promhttp_start_daemon(MHD_USE_SELECT_INTERNALLY, 8000, NULL, NULL);
 
   if (promtest_daemon == NULL) return 1;
   else return 0;