make private if not part of provider interface

providers/bitcoin/providerImpl.go

@@ -51,7 +51,7 @@ func (p *Provider) GetBalances() ([]int, []string, error) {
 	ynabAccountIDs := make([]string, 0)
 	var satoshiBalance int
 	for _, bitcoinAddress := range p.bitcoinAddresses {
-		addressResponse, err := p.client.GetAddress(bitcoinAddress)
+		addressResponse, err := p.client.getAddress(bitcoinAddress)
 		if err != nil {
 			return balances, ynabAccountIDs, fmt.Errorf("failed to get bitcoin address '%s': %v", bitcoinAddress, err)
 		}