Add concurrency

concurrency/cmd/csp/csv.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"encoding/csv"
+	"io"
+	"os"
+	"sync"
+	"time"
+)
+
+// The free tier of the OpenWeatherMap API allows for 60 requests per minute.
+// ∴ we limit our requests to 1 per second.
+var interval = 1 * time.Second
+
+func processCSV(
+	file *os.File, ztchan chan *ZipTemp,
+) {
+	var (
+		limiter = time.Tick(interval)
+		wg      sync.WaitGroup
+	)
+
+	reader := csv.NewReader(file)
+	for {
+		record, err := reader.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			panic(err)
+		}
+
+		<-limiter
+
+		wg.Add(1)
+		go getZipTemp(&wg, record, ztchan)
+	}
+
+	wg.Wait()
+	close(ztchan)
+}