implement rudimentary caching for yahoo finance to avoid http 429 rate limiting

providers/staticjsonYahooFinance/providerImpl.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"io"
 	"os"
-	"time"
 )
 
 type security struct {
@@ -48,6 +47,8 @@ func (p *Provider) Configure() error {
 		return fmt.Errorf("failed to create new client: %v", err)
 	}
 
+	chartCache = make(map[string]chartCacheEntry)
+
 	return nil
 }
 
@@ -63,7 +64,6 @@ func (p *Provider) GetBalances() ([]int, []string, error) {
 				return balances, ynabAccountIDs, fmt.Errorf("failed to get quote for security with symbol '%s': %v", p.data.Accounts[i].Securities[j].Symbol, err)
 			}
 			balance += price * p.data.Accounts[i].Securities[j].Quantity
-			time.Sleep(time.Second) // Disgusting way to avoid HTTP 429 rate limiting
 		}
 		balances = append(balances, balance)
 		ynabAccountIDs = append(ynabAccountIDs, p.data.Accounts[i].YnabAccountID)