Update to go 1.17, remove duplicate go-mail

- update module to go 1.17 level
- ran go mod tidy
- bump go version in Jenkinsfile
- drop github.com/go-mail/mail

Jenkinsfile

@@ -18,7 +18,7 @@ pipeline {
     agent any
 
     tools {
-        go "go-1.16"
+        go "go-1.17"
     }
 
     stages {

go.mod

@@ -1,10 +1,9 @@
 module git.cacert.org/cacert-boardvoting
 
-go 1.16
+go 1.17
 
 require (
 	github.com/Masterminds/sprig/v3 v3.2.2
-	github.com/go-mail/mail v2.3.1+incompatible
 	github.com/golang-migrate/migrate/v4 v4.14.2-0.20201125065321-a53e6fc42574
 	github.com/google/uuid v1.2.0 // indirect
 	github.com/gorilla/csrf v1.7.0
@@ -22,6 +21,17 @@ require (
 	golang.org/x/crypto v0.0.0-20210314154223-e6e6c4f2bb5b // indirect
 	golang.org/x/sys v0.0.0-20210313202042-bd2e13477e9c // indirect
 	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
-	gopkg.in/mail.v2 v2.3.1 // indirect
+	gopkg.in/mail.v2 v2.3.1
 	gopkg.in/yaml.v2 v2.4.0
 )
+
+require (
+	github.com/Masterminds/goutils v1.1.1 // indirect
+	github.com/Masterminds/semver/v3 v3.1.1 // indirect
+	github.com/andybalholm/brotli v1.0.1 // indirect
+	github.com/gorilla/securecookie v1.1.1 // indirect
+	github.com/mitchellh/reflectwalk v1.0.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/shopspring/decimal v1.2.0 // indirect
+	github.com/spf13/cast v1.3.1 // indirect
+)

go.sum

@@ -89,8 +89,6 @@ github.com/fsouza/fake-gcs-server v1.17.0/go.mod h1:D1rTE4YCyHFNa99oyJJ5HyclvN/0
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20200222043503-6f7a984d4dc4/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
-github.com/go-mail/mail v2.3.1+incompatible h1:UzNOn0k5lpfVtO31cK3hn6I4VEVGhe3lX8AJBAxXExM=
-github.com/go-mail/mail v2.3.1+incompatible/go.mod h1:VPWjmmNyRsWXQZHVHT3g0YbIINUkSmuKOiLIDkWbL6M=
 github.com/go-sql-driver/mysql v1.4.0/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG5ZlKdlhCg5w=
 github.com/go-sql-driver/mysql v1.5.0 h1:ozyZYNQW3x3HtqT1jira07DN2PArx2v7/mN66gGcHOs=
 github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=

notifications.go

@@ -23,7 +23,7 @@ import (
 	"text/template"
 
 	"github.com/Masterminds/sprig/v3"
-	"github.com/go-mail/mail"
+	"gopkg.in/mail.v2"
 
 	log "github.com/sirupsen/logrus"
 )