refactor exchange rates data backend, supports multi data source, supports timeout

pkg/exchangerates/exchange_rates_datasource_container.go

@@ -0,0 +1,26 @@
+package exchangerates
+
+import (
+	"github.com/mayswind/lab/pkg/errs"
+	"github.com/mayswind/lab/pkg/settings"
+)
+
+// ExchangeRatesDataSourceContainer contains the current exchange rates data source
+type ExchangeRatesDataSourceContainer struct {
+	Current ExchangeRatesDataSource
+}
+
+// Initialize a exchange rates data source container singleton instance
+var (
+	Container = &ExchangeRatesDataSourceContainer{}
+)
+
+// InitializeExchangeRatesDataSource initializes the current exchange rates data source according to the config
+func InitializeExchangeRatesDataSource(config *settings.Config) error {
+	if config.ExchangeRatesDataSource == settings.EuroCentralBankDataSource {
+		Container.Current = &EuroCentralBankDataSource{}
+		return nil
+	}
+
+	return errs.ErrInvalidExchangeRatesDataSource
+}