'AWS SAM golang lambda localhost connection refused to postgres

I'm unable to connect an AWS SAM lambda function to a local postgres instance. I'll be specific in a moment, but first let me say that the same code works for my coworker and that I've tried using Postgres within a docker container as well as installed manually. To simplify the problem I started over with the SAM helloworld golang example and added the following:

import (
  _ "github.com/lib/pq"
  "database/sql"
)
.
.
.
const (
    host     = "localhost"
    port     = 5432
    user     = "postgres"
    password = "postgres"
    dbname   = "postgres"
)
.
.
.
.
psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+
    "password=%s dbname=%s sslmode=disable",
    host, port, user, password, dbname)

db, err := sql.Open("postgres", psqlInfo)

if err != nil {
    panic(err)
}
defer db.Close()

err = db.Ping()
if err != nil {
    panic(err)
}

fmt.Println("Successfully connected!")

And I get the following error:

dial tcp 127.0.0.1:5432: connect: connection refused: OpError
[{"path":"github.com/aws/[email protected]/lambda/function.go","line":35,"label":"(*Function).Invoke.func1"},{"path":"runtime/panic.go","line":969,"label":"gopanic"},{"path":"hello-world/main.go","line":67,"label":"handler"},{"path":"reflect/value.go","line":475,"label":"Value.call"},{"path":"reflect/value.go","line":336,"label":"Value.Call"},{"path":"github.com/aws/[email protected]/lambda/handler.go","line":124,"label":"NewHandler.func1"},{"path":"github.com/aws/[email protected]/lambda/handler.go","line":24,"label":"lambdaHandler.Invoke"},{"path":"github.com/aws/[email protected]/lambda/function.go","line":67,"label":"(*Function).Invoke"},{"path":"reflect/value.go","line":475,"label":"V
alue.call"},{"path":"reflect/value.go","line":336,"label":"Value.Call"},{"path":"net/rpc/server.go","line":377,"label":"(*service).call"},{"path":"runtime/asm_amd64.s","line":1374,"label":"goexit"}]

SAM CLI, version 1.21.1

I've now tried this on two machines and get the same error. Is there there something that I'm just missing there? I can confirm that the the database is receiving connections fine. I hit it every day from a node app. Also, I can build the golang code outside of SAM and it will work fine. So there's something with my SAM setup that's wrong.

postgresqlgoaws-lambdaaws-sam-clisam


Solution 1:[1]

Figured it out. Within the lambda I needed to set the postgres connection string to hit host.docker.internal

Solution 2:[2]

I spend a lot of time figuring out how to connect using AWS SAM to a local Postgres and finally found that changing the dbhostname from localhost to host.docker.internal works.

connectionString = 'postgresql://dbuser:[email protected]:5432/dbname';

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Etwillms
Solution 2 lpaulmp

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