Use own slack fork to fix #937 (#943)

vendor/github.com/nlopes/slack/block_conv.go

@@ -61,7 +61,7 @@ func (b *Blocks) UnmarshalJSON(data []byte) error {
 		case "section":
 			block = &SectionBlock{}
 		default:
-			return errors.New("unsupported block type")
+			block = &UnknownBlock{}
 		}
 
 		err = json.Unmarshal(r, block)
@@ -127,7 +127,7 @@ func (b *BlockElements) UnmarshalJSON(data []byte) error {
 		case "static_select", "external_select", "users_select", "conversations_select", "channels_select":
 			blockElement = &SelectBlockElement{}
 		default:
-			return errors.New("unsupported block element type")
+			blockElement = &UnknownBlockElement{}
 		}
 
 		err = json.Unmarshal(r, blockElement)

vendor/github.com/nlopes/slack/block_element.go

@@ -62,6 +62,20 @@ type BlockElements struct {
 	ElementSet []BlockElement `json:"elements,omitempty"`
 }
 
+// UnknownBlockElement any block element that this library does not directly support.
+// See the "Rich Elements" section at the following URL:
+// https://api.slack.com/changelog/2019-09-what-they-see-is-what-you-get-and-more-and-less
+// New block element types may be introduced by Slack at any time; this is a catch-all for any such block elements.
+type UnknownBlockElement struct {
+	Type     MessageElementType `json:"type"`
+	Elements BlockElements
+}
+
+// ElementType returns the type of the Element
+func (s UnknownBlockElement) ElementType() MessageElementType {
+	return s.Type
+}
+
 // ImageBlockElement An element to insert an image - this element can be used
 // in section and context blocks only. If you want a block with only an image
 // in it, you're looking for the image block.

vendor/github.com/nlopes/slack/block_unknown.go

@@ -0,0 +1,14 @@
+package slack
+
+// UnknownBlock represents a block type that is not yet known. This block type exists to prevent Slack from introducing
+// new and unknown block types that break this library.
+type UnknownBlock struct {
+	Type     MessageBlockType `json:"type"`
+	BlockID  string           `json:"block_id,omitempty"`
+	Elements BlockElements    `json:"elements"`
+}
+
+// BlockType returns the type of the block
+func (b UnknownBlock) BlockType() MessageBlockType {
+	return b.Type
+}

vendor/github.com/nlopes/slack/go.mod

@@ -1,4 +1,4 @@
-module github.com/nlopes/slack
+module github.com/matterbridge/slack
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect