add duration output

01/main.go

@@ -5,11 +5,16 @@ import (
 	"fmt"
 	"os"
 	"strconv"
+	"time"
 )
 
 func main() {
+	start := time.Now()
 	partOne()
+	duration := time.Since(start)
 	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
 }
 
 // [...] they need you to find the two entries that sum to 2020 and then multiply those two numbers together.