fix strings.ToLower wrong replacement in abi encoding, was lower casing tag names (#224)

Author: cyberhorsey

abi/encode.go

@@ -294,12 +294,10 @@ func mapFromStruct(v reflect.Value) (reflect.Value, error) {
 			continue
 		}
 
-		name := f.Name
+		name := strings.ToLower(f.Name)
 		if tagValue != "" {
 			name = tagValue
 		}
-
-		name = strings.ToLower(name)
 		if _, ok := res[name]; !ok {
 			res[name] = v.Field(i).Interface()
 		}

abi/encoding_test.go

@@ -706,3 +706,29 @@ func TestEncodingStruct(t *testing.T) {
 		t.Fatal("bad")
 	}
 }
+
+func TestEncodingStruct_camcelCase(t *testing.T) {
+	typ := MustNewType("tuple(address aA, uint256 b)")
+
+	type Obj struct {
+		A ethgo.Address `abi:"aA"`
+		B *big.Int
+	}
+	obj := Obj{
+		A: ethgo.Address{0x1},
+		B: big.NewInt(1),
+	}
+
+	encoded, err := typ.Encode(&obj)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var obj2 Obj
+	if err := typ.DecodeStruct(encoded, &obj2); err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(obj, obj2) {
+		t.Fatal("bad")
+	}
+}