internal/codegen/golang: tweak tag formatting

Rather than inserting the colon at tag construction time,
insert it at tag formatting time.

This makes the input look a bit more natural.
This matters more, as we are about to add another,
more distant, place where we insert tags.

Author: josharian

internal/codegen/golang/field.go

@@ -19,7 +19,7 @@ type Field struct {
 func (gf Field) Tag() string {
 	tags := make([]string, 0, len(gf.Tags))
 	for key, val := range gf.Tags {
-		tags = append(tags, fmt.Sprintf("%s\"%s\"", key, val))
+		tags = append(tags, fmt.Sprintf("%s:\"%s\"", key, val))
 	}
 	if len(tags) == 0 {
 		return ""

internal/codegen/golang/result.go

@@ -74,10 +74,10 @@ func buildStructs(req *plugin.CodeGenRequest) []Struct {
 			for _, column := range table.Columns {
 				tags := map[string]string{}
 				if req.Settings.Go.EmitDbTags {
-					tags["db:"] = column.Name
+					tags["db"] = column.Name
 				}
 				if req.Settings.Go.EmitJsonTags {
-					tags["json:"] = JSONTagName(column.Name, req.Settings)
+					tags["json"] = JSONTagName(column.Name, req.Settings)
 				}
 				s.Fields = append(s.Fields, Field{
 					Name:    StructName(column.Name, req.Settings),
@@ -283,10 +283,10 @@ func columnsToStruct(req *plugin.CodeGenRequest, name string, columns []goColumn
 		}
 		tags := map[string]string{}
 		if req.Settings.Go.EmitDbTags {
-			tags["db:"] = tagName
+			tags["db"] = tagName
 		}
 		if req.Settings.Go.EmitJsonTags {
-			tags["json:"] = JSONTagName(tagName, req.Settings)
+			tags["json"] = JSONTagName(tagName, req.Settings)
 		}
 		gs.Fields = append(gs.Fields, Field{
 			Name:   fieldName,