gnu: Add go-github-com-emersion-go-smtp.

* gnu/packages/golang.scm (go-github-com-emersion-go-smtp): New
  variable.

Signed-off-by: Raghav Gururajan <rg@raghavgururajan.name>

gnu/packages/golang.scm

@@ -6669,6 +6669,30 @@ can be used to build IMAP clients and servers.")
 @code{go-github-com-emersion-go-imap}.")
     (license license:expat)))
 
+(define-public go-github-com-emersion-go-smtp
+  (package
+    (name "go-github-com-emersion-go-smtp")
+    (version "0.15.0")
+    (source (origin
+              (method git-fetch)
+              (uri (git-reference
+                    (url "https://github.com/emersion/go-smtp")
+                    (commit (string-append "v" version))))
+              (file-name (git-file-name name version))
+              (sha256
+               (base32
+                "1vhc0vpjd4yhxk6wrh01sdpi7nprjn98s46yy82xwlkm0cskl0h7"))))
+    (build-system go-build-system)
+    (arguments
+     (list #:import-path "github.com/emersion/go-smtp"))
+    (propagated-inputs (list go-github-com-emersion-go-sasl))
+    (home-page "https://github.com/emersion/go-smtp")
+    (synopsis "SMTP implementation for Go")
+    (description
+     "This package implements the Simple Mail Transfer Protocol as
+defined by RFC 5321.")
+    (license license:expat)))
+
 (define-public go-github-com-emersion-go-sasl
   (let ((commit "0b9dcfb154ac3d7515b08bc2691a0332800edfe9")
         (revision "1"))