feat: makefile, git version number

projects/greenlight/Makefile

@@ -82,8 +82,10 @@ vendor:
 #
 # ==================================================================================== #
 
-current_time = $(shell date -u +"%Y-%m-%dT%H:%M:%S%z")
-linker_flags = '-s -X main.buildTime=${current_time}'
+current_time = $(shell date --iso-8601=seconds)
+git_description = $(shell git describe --always --dirty)
+linker_flags = '-s -X main.buildTime=${current_time} -X main.version=${git_description}
+
 
 ## build/api: build the cmd/api application
 .PHONY: build/api

projects/greenlight/cmd/api/main.go

@@ -19,14 +19,10 @@ import (
 	"greenlight.debuggingjon.dev/internal/mailer"
 )
 
-// Declare a string containing the application version number. Later in the book we'll
-// generate this automatically at build time, but for now we'll just store the version
-// number as a hard-coded global constant.
-const version = "1.0.0"
-
-// Create a buildTime variable to hold the executable binary build time. Note that this
-// must be a string type, as the -X linker flag will only work with string variables.
-var buildTime string
+var (
+	buildTime string
+	version   string
+)
 
 // Define a config struct to hold all the configuration settings for our application.
 // For now, the only configuration settings will be the network port that we want the