Re-implement a solution for the first day 1 puzzle, move common code into a library package.

2018/day01-2.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"internal/calibration"
+)
+
+// Provide a filename as input, get the result on stdout
+func main() {
+	x := 0
+	found := false
+	seen := calibration.Set{0: struct{}{}}
+
+	for {
+		x, found = calibration.ScanFrequencies(os.Args[1], &seen, x)
+		if found {
+			break
+		}
+		fmt.Println("All frequencies scanned, repeating...")
+	}
+
+	fmt.Println("Repeat frequency detected, calibration complete: ", x)
+}