Slack Web API

Core API Pattern

All Web API methods follow this pattern:

result, err := api.MethodName(params...) if err != nil { // Handle error (rate limits, permissions, etc.) return err } // Use result

Messaging Operations

Send Simple Text Message

channelID := "C1234567890" text := "Hello, Slack!"

_, _, err := api.PostMessage( channelID, slack.MsgOptionText(text, false), )

Send Message with Block Kit

headerText := slack.NewTextBlockObject("mrkdwn", "Deployment Complete", false, false) headerBlock := slack.NewSectionBlock(headerText, nil, nil)

divider := slack.NewDividerBlock()

bodyText := slack.NewTextBlockObject("mrkdwn", "Version 2.1.0 deployed successfully", false, false) bodyBlock := slack.NewSectionBlock(bodyText, nil, nil)

_, _, err := api.PostMessage( channelID, slack.MsgOptionBlocks(headerBlock, divider, bodyBlock), )

See web-api-messaging.md for comprehensive messaging patterns including threading, updates, and ephemeral messages.

Channel Operations

Create a Channel

channelName := "project-updates" isPrivate := false

channel, err := api.CreateConversation(channelName, isPrivate) if err != nil { return err } fmt.Printf("Created channel: %s (ID: %s)\n", channel.Name, channel.ID)

List Channels

params := &slack.GetConversationsParameters{ Types: []string{"public_channel"}, Limit: 100, }

channels, nextCursor, err := api.GetConversations(params)

See web-api-channels.md for channel management, invites, and metadata operations.

User Operations

Get User Information

user, err := api.GetUserInfo("U1234567890") if err != nil { return err }

fmt.Printf("User: %s (%s)\n", user.Profile.RealName, user.Profile.Email)

List All Users

users, err := api.GetUsers() if err != nil { return err }

for _, user := range users { fmt.Printf("- %s (%s)\n", user.Name, user.ID) }

See web-api-users.md for user presence, profiles, and groups.

File Operations

Upload a File

params := slack.FileUploadParameters{ File: "report.pdf", Channels: []string{"C1234567890"}, Title: "Monthly Report", }

file, err := api.UploadFile(params) if err != nil { return err }

See web-api-files.md for file downloads, sharing, and multi-part uploads.

Block Kit Integration

Block Kit allows rich, interactive messages. See block-kit-integration.md for:

• Section blocks with text, images, and accessories

• Interactive buttons and select menus

• Input blocks for forms

• Complete layout patterns

Error Handling

Rate Limiting

_, _, err := api.PostMessage(channelID, slack.MsgOptionText(text, false)) if err != nil { if rateLimitErr, ok := err.(*slack.RateLimitedError); ok { time.Sleep(rateLimitErr.RetryAfter) // Retry operation } return err }

Common Error Types

• slack.RateLimitedError

• Too many requests

• Permission errors - Missing scopes

• channel_not_found

• Invalid channel ID

• invalid_auth

• Token issues

Pagination

For operations returning large result sets, use cursor-based pagination:

cursor := "" for { params := &slack.GetConversationsParameters{ Cursor: cursor, Limit: 100, }

channels, nextCursor, err := api.GetConversations(params)
if err != nil {
    return err
}

// Process channels...

if nextCursor == "" {
    break
}
cursor = nextCursor

}

See pagination-patterns.md for advanced pagination strategies.

Common Pitfalls

• Not handling rate limits (use exponential backoff)

• Hardcoding channel/user IDs (use lookups or environment variables)

• Forgetting to escape user input in messages

• Not validating Bot Token scopes match required permissions

• Using blocking operations in high-throughput scenarios