Added file env support

entrypoint.sh

@@ -1,5 +1,33 @@
 #!/bin/bash
 
+# usage: file_env VAR [DEFAULT]
+#    ie: file_env 'XYZ_DB_PASSWORD' 'example'
+# (will allow for "$XYZ_DB_PASSWORD_FILE" to fill in the value of
+#  "$XYZ_DB_PASSWORD" from a file, especially for Docker's secrets feature)
+file_env() {
+	  local var="$1"
+	  local fileVar="${var}_FILE"
+	  local def="${2:-}"
+	  if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
+		    echo >&2 "error: both $var and $fileVar are set (but are exclusive)"
+		    exit 1
+	  fi
+	  local val="$def"
+	  if [ "${!var:-}" ]; then
+		    val="${!var}"
+	  elif [ "${!fileVar:-}" ]; then
+		    val="$(< "${!fileVar}")"
+	  fi
+	  export "$var"="$val"
+	  unset "$fileVar"
+}
+
+# File envs
+file_env 'GOOGLE_CLIENT_ID'
+file_env 'GOOGLE_CLIENT_SECRET'
+file_env 'SLACK_SECRET'
+file_env 'PG_ENV_POSTGRES_PASSWORD'
+
 echo $@;
 if [ "$#" -ne 0 ]
 then