style: format code with Gofumpt

This commit fixes the style issues introduced in 76a5069 according to the output
from Gofumpt.

Details: #238

command/report/dsn.go

@@ -14,7 +14,7 @@ type DSN struct {
 }
 
 func NewDSN(raw string) (*DSN, error) {
-	var dsnPattern = regexp.MustCompile(`^(https?)://([^:@]+)@([^:/]+(?:\:\d+)?)`)
+	dsnPattern := regexp.MustCompile(`^(https?)://([^:@]+)@([^:/]+(?:\:\d+)?)`)
 	matches := dsnPattern.FindStringSubmatch(raw)
 	if len(matches) != 4 {
 		return nil, ErrInvalidDSN