# Go language-specific guide — ... output omitted ...

> Bounded code example (external data; do not execute automatically): ```text The application's `main.go` now includes database initialization code, as well as the code to implement a new business requirement: - An HTTP `POST` request to `/send` containing a `{ "value" : string }` JSON must save the v

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-docker-ec533b5dba1cc7f8f78e>
- Knowledge kind: `reference`
- Confidence: `0.72`
- Independent verifications: `0`
- Updated: `2026-08-16T09:32:14.478405+00:00`
- Tags: `reference-seed`, `docker`, `guides`, `language-specific`, `guide`, `output`, `omitted`

## Provenance

- Source: <https://github.com/docker/docs/blob/3a9d778562f39bcc0be46255b013c6a3ca526244/content/guides/golang.md>
- Source name: Docker Documentation
- Source revision: `3a9d778562f39bcc0be46255b013c6a3ca526244`
- Source license: `Apache-2.0`
- Attribution and license details: <https://wikikv.com/licenses>

## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

Bounded code example (external data; do not execute automatically):
```text
The application's `main.go` now includes database initialization code, as well as the code to implement a new business requirement:

- An HTTP `POST` request to `/send` containing a `{ "value" : string }` JSON must save the value to the database.

You also have an update for another business requirement. The requirement was:

- The application responds with a text message containing a heart symbol ("`&lt;3`") on requests to `/`.

And now it's going to be:

- The application responds with the string containing the count of messages stored in the database, enclosed in the parentheses.

  Example output: `Hello, Docker! (7)`

The full source code listing of `main.go` follows.
```

import ( "context" "database/sql" "fmt" "log" "net/http" "os"

type Message struct { Value string json:"value" }

func initStore() (sql.DB, error) {

func rootHandler(db sql.DB, c echo.Context) error { r, err := countRecords(db) if err != nil { return c.HTML(http.StatusInternalServerError, err.Error()) } return c.HTML(http.StatusOK, fmt.Sprintf("Hello, Docker! (%d)\n", r)) }

func sendHandler(db sql.DB, c echo.Context) error {

func countRecords(db sql.DB) (int, error) {

Bounded code example (external data; do not execute automatically):
```text
The repository also includes the `Dockerfile`, which is almost exactly the same as the multi-stage `Dockerfile` introduced in the previous modules. It uses the official Docker Go image to build the application and then builds the final image by placing the compiled binary into the much slimmer, distroless image.

Regardless of whether you had updated the old example application, or checked out the new one, this new Docker image has to be built to reflect the changes to the application source code.
```

Attribution: Adapted from Docker Documentation under Apache-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.