GoをHerokuにデプロイしたが、H13errorで接続できない

Question

goをherokuで動かそうとしていますが、H13errorを起こし、うまくデプロイできません。
heroku logs --tail後のログを掲載させていただきます。
ポート接続・DB接続ができず、timeoutを起こしているかと思われるのですが、どういった原因が考えられますでしょうか。
(ローカルでDBが繋がることは確認し、ログにポート番号の記載もあるのですが...)

原因が分からず困っております。
なにかアドバイスをいただけると幸いです。

<中略>
2021-03-08T21:46:08.000000+00:00 app[api]: Build started by user [e-mail]
2021-03-08T21:46:26.586570+00:00 app[api]: Release v37 created by user [e-mail]
2021-03-08T21:46:26.586570+00:00 app[api]: Deploy 89f1ed47 by user [e-mail]
2021-03-08T21:46:27.216299+00:00 heroku[web.1]: Restarting
2021-03-08T21:46:27.231381+00:00 heroku[web.1]: State changed from up to starting
2021-03-08T21:46:27.974556+00:00 heroku[web.1]: Starting process with command `sharefull`
2021-03-08T21:46:28.987747+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2021-03-08T21:46:29.215654+00:00 heroku[web.1]: Process exited with status 143
2021-03-08T21:46:30.302424+00:00 heroku[web.1]: State changed from starting to up
2021-03-08T21:46:31.000000+00:00 app[api]: Build started by user [e-mail]
2021-03-08T21:46:49.314187+00:00 app[api]: Deploy 89f1ed47 by user [e-mail]
2021-03-08T21:46:49.314187+00:00 app[api]: Release v38 created by user [e-mail]
2021-03-08T21:46:49.494448+00:00 heroku[web.1]: Restarting
2021-03-08T21:46:49.512498+00:00 heroku[web.1]: State changed from up to starting
2021-03-08T21:46:50.374267+00:00 heroku[web.1]: Starting process with command `sharefull`
2021-03-08T21:46:51.137331+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2021-03-08T21:46:51.252244+00:00 heroku[web.1]: Process exited with status 143
2021-03-08T21:46:52.000000+00:00 app[api]: Build succeeded
2021-03-08T21:46:54.719178+00:00 heroku[web.1]: State changed from starting to up
2021-03-08T21:47:20.000000+00:00 app[api]: Build succeeded
2021-03-08T21:47:21.168172+00:00 app[web.1]: 2021/03/08 21:47:21 server.go:3095: http: panic serving 10.93.170.169:28556: runtime error: invalid memory address or nil pointer dereference
2021-03-08T21:47:21.168244+00:00 app[web.1]: goroutine 22 [running]:
2021-03-08T21:47:21.168249+00:00 app[web.1]: net/http.(*conn).serve.func1(0xc0000ac280)
2021-03-08T21:47:21.168264+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:1801 +0x147
2021-03-08T21:47:21.168264+00:00 app[web.1]: panic(0x991fe0, 0xde8980)
2021-03-08T21:47:21.168265+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/runtime/panic.go:975 +0x47a
2021-03-08T21:47:21.168270+00:00 app[web.1]: database/sql.(*DB).conn(0x0, 0xae86c0, 0xc000026048, 0x4cff01, 0xa2bc64, 0x9, 0xc0003072f0)
2021-03-08T21:47:21.168270+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/database/sql/sql.go:1190 +0x41
2021-03-08T21:47:21.168276+00:00 app[web.1]: database/sql.(*DB).query(0x0, 0xae86c0, 0xc000026048, 0xa4bcd9, 0xb5, 0x0, 0x0, 0x0, 0x1, 0xc00009e1d0, ...)
2021-03-08T21:47:21.168277+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/database/sql/sql.go:1616 +0x66
2021-03-08T21:47:21.168281+00:00 app[web.1]: database/sql.(*DB).QueryContext(0x0, 0xae86c0, 0xc000026048, 0xa4bcd9, 0xb5, 0x0, 0x0, 0x0, 0x2, 0xc0003075e0, ...)
2021-03-08T21:47:21.168282+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/database/sql/sql.go:1598 +0xd1
2021-03-08T21:47:21.168282+00:00 app[web.1]: database/sql.(*DB).Query(...)
2021-03-08T21:47:21.168290+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/database/sql/sql.go:1612
2021-03-08T21:47:21.168290+00:00 app[web.1]: github.com/keigooba/sharefull/app/models.GetWorks(0xc009c4ba4a0100c4, 0x69939a146, 0xdfb3e0, 0xa2c1dc, 0xa)
2021-03-08T21:47:21.168290+00:00 app[web.1]: /tmp/tmp.NN04IG416B/.go/src/github.com/keigooba/sharefull/app/models/works.go:65 +0x85
2021-03-08T21:47:21.168291+00:00 app[web.1]: github.com/keigooba/sharefull/app/controllers.index(0xae67c0, 0xc0000d00e0, 0xc0000c8200)
2021-03-08T21:47:21.168291+00:00 app[web.1]: /tmp/tmp.NN04IG416B/.go/src/github.com/keigooba/sharefull/app/controllers/r_main.go:18 +0x91
2021-03-08T21:47:21.168291+00:00 app[web.1]: net/http.HandlerFunc.ServeHTTP(0xa52118, 0xae67c0, 0xc0000d00e0, 0xc0000c8200)
2021-03-08T21:47:21.168292+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:2042 +0x44
2021-03-08T21:47:21.168292+00:00 app[web.1]: net/http.(*ServeMux).ServeHTTP(0xdfb1a0, 0xae67c0, 0xc0000d00e0, 0xc0000c8200)
2021-03-08T21:47:21.168292+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:2417 +0x1ad
2021-03-08T21:47:21.168292+00:00 app[web.1]: net/http.serverHandler.ServeHTTP(0xc0000d0000, 0xae67c0, 0xc0000d00e0, 0xc0000c8200)
2021-03-08T21:47:21.168293+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:2843 +0xa3
2021-03-08T21:47:21.168293+00:00 app[web.1]: net/http.(*conn).serve(0xc0000ac280, 0xae8680, 0xc000090380)
2021-03-08T21:47:21.168293+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:1925 +0x8ad
2021-03-08T21:47:21.168294+00:00 app[web.1]: created by net/http.(*Server).Serve
2021-03-08T21:47:21.168294+00:00 app[web.1]: /tmp/codon/tmp/cache/go1.15.8/go/src/net/http/server.go:2969 +0x36c
2021-03-08T21:47:21.168314+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/" host=sharefull.herokuapp.com request_id=0aa6d261-aed0-4506-8785-cd8b577180a5 fwd="36.11.229.139" dyno=web.1 connect=2ms service=2ms status=503 bytes=0 protocol=https
2021-03-08T21:47:21.496481+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/favicon.ico" host=sharefull.herokuapp.com request_id=8dd6eab8-9ec0-4c94-a4d2-0e7f06e86de6 fwd="36.11.229.139" dyno=web.1 connect=1ms service=1ms status=503 bytes=0 protocol=https
2021-03-08T21:47:21.498313+00:00 app[web.1]: 2021/03/08 21:47:21 server.go:3095: http: panic serving 10.16.250.243:10880: runtime error: invalid memory address or nil pointer dereference
2021-03-08T21:47:21.498346+00:00 app[web.1]: goroutine 9 [running]:
2021-03-08T21:47:21.498349+00:00 app[web.1]: net/http.(*conn).serve.func1(0xc00011f040)
<中略>

ポート設定

port := os.Getenv("PORT")
if port != "" {
return http.ListenAndServe(":"+port, nil)
}

DB設定

Db, err := sql.Open("postgres", os.Getenv("DATABASE_URL"))
if err != nil {
 log.Fatalln(err)
}