GOLANG: No stacks found for "custom" on Azure Functions v4

Question

GOLANG: No stacks found for "custom" on Azure Functions v4

Ken Just-Ken 0

Following the instructions on learn.microsoft.com for creating an Azure Function written in Golang, the instructions fail here: https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-vs-code-other?tabs=go%2Cmacos#create-the-function-app-in-azure

...at step 3/3 with the message "No stacks found for "custom" on Azure Functions v4".

This appears to be in reference to the value in local.settings.json for "FUNCTIONS_WORKER_RUNTIME": "custom"

...but changing that to other values did not result in success or a different error message.

Is this an issue with Azure Functions? Or is it an issue with Azure Functions Core Tools?

Please provide a work-around OR document that Golang is not supported.

Thanks!

Ken

Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-10T07:12:07.14+00:00
Hi Ken Just-Ken,

The error "No stacks found for 'custom' on Azure Functions v4" means that Azure Functions Core Tools can't find the "custom" runtime needed for using Golang with custom handlers.

Make sure you have the latest version of Azure Functions Core Tools installed, as updates may fix recognition problems.

Verify that your host.json and local.settings.json files are set up correctly for a custom handler.

Ensure that your Azure Function App is set to use a custom runtime when you create it in the Azure portal.

Remember that Golang is supported in Azure Functions through custom handlers, not as a built-in runtime.

For more details, see Azure Functions custom handlers.

I hope this is helpful! Feel free to reach out if you have any more questions or need further assistance.
Ken Just-Ken 0 Reputation points

2025-03-10T20:06:46.0966667+00:00

Hi Shireesha,

I double-checked and I do have the latest version of Azure Functions Core Tools installed.

My host.json and local.settings.json files are set up the same as those in the examples provided for a custom handler. However, the example has "FUNCTIONS_WORKER_RUNTIME" : "Custom" while mine had the value as "custom". I changed mine to "Custom" and I'm still getting the same error. I tried changing that value to various other strings and I'm still getting the same error that No stacks found for "custom" on Azure Functions v4.

It appears that I'm missing a step in the process and that the value "custom" is being cached?

Just now, I closed VSCode, restarted it and created a new project from scratch, again following the steps at https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-vs-code-other?tabs=go%2Cmacos.

I'm still getting the exact same error message.

Any suggestions for how to further troubleshoot this are greatly appreciated.

Thanks!

Ken
Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-11T05:55:20.4966667+00:00
Hi Ken Just-Ken,

It seems that the problem might be linked to the configuration of your Azure Function for custom handlers. Here are some steps you can take to troubleshoot the issue further:

Check Azure Function App Settings: Make sure that when you create the Function App in the Azure portal, it is configured to use a custom runtime.

Verify Configuration Files: Take a moment to double-check that your host.json and local.settings.json files are set up correctly. The FUNCTIONS_WORKER_RUNTIME should be specified as "custom" (case-sensitive).

Update Core Tools: Although you mentioned that you have the latest version, consider reinstalling Azure Functions Core Tools to eliminate any potential installation issues.

Clear Cache: Sometimes, local cache issues can cause problems. Try clearing the Azure Functions Core Tools cache by running:

func azure functionapp fetch-app-settings <YourFunctionAppName>

a simple Azure Function project by closely following the official documentation to rule out any project-specific issues.

I hope this answers your query! Let me know if you require any additional help or clarification.
Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-12T06:13:10.1433333+00:00

Hi @Ken Just-Ken ,

just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.

Your answer

Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-10T07:12:07.14+00:00

Hi Ken Just-Ken,

The error "No stacks found for 'custom' on Azure Functions v4" means that Azure Functions Core Tools can't find the "custom" runtime needed for using Golang with custom handlers.

Make sure you have the latest version of Azure Functions Core Tools installed, as updates may fix recognition problems.

Verify that your host.json and local.settings.json files are set up correctly for a custom handler.

Ensure that your Azure Function App is set to use a custom runtime when you create it in the Azure portal.

Remember that Golang is supported in Azure Functions through custom handlers, not as a built-in runtime.

For more details, see Azure Functions custom handlers.

I hope this is helpful! Feel free to reach out if you have any more questions or need further assistance.
Ken Just-Ken 0 Reputation points

2025-03-10T20:06:46.0966667+00:00

Hi Shireesha,

I double-checked and I do have the latest version of Azure Functions Core Tools installed.

My host.json and local.settings.json files are set up the same as those in the examples provided for a custom handler. However, the example has "FUNCTIONS_WORKER_RUNTIME" : "Custom" while mine had the value as "custom". I changed mine to "Custom" and I'm still getting the same error. I tried changing that value to various other strings and I'm still getting the same error that No stacks found for "custom" on Azure Functions v4.

It appears that I'm missing a step in the process and that the value "custom" is being cached?

Just now, I closed VSCode, restarted it and created a new project from scratch, again following the steps at https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-vs-code-other?tabs=go%2Cmacos.

I'm still getting the exact same error message.

Any suggestions for how to further troubleshoot this are greatly appreciated.

Thanks!

Ken
Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-11T05:55:20.4966667+00:00

Hi Ken Just-Ken,

It seems that the problem might be linked to the configuration of your Azure Function for custom handlers. Here are some steps you can take to troubleshoot the issue further:

Check Azure Function App Settings: Make sure that when you create the Function App in the Azure portal, it is configured to use a custom runtime.

Verify Configuration Files: Take a moment to double-check that your host.json and local.settings.json files are set up correctly. The FUNCTIONS_WORKER_RUNTIME should be specified as "custom" (case-sensitive).

Update Core Tools: Although you mentioned that you have the latest version, consider reinstalling Azure Functions Core Tools to eliminate any potential installation issues.

Clear Cache: Sometimes, local cache issues can cause problems. Try clearing the Azure Functions Core Tools cache by running:

func azure functionapp fetch-app-settings <YourFunctionAppName>

a simple Azure Function project by closely following the official documentation to rule out any project-specific issues.

I hope this answers your query! Let me know if you require any additional help or clarification.
Shireesha Eeraboina 1,980 Reputation points Microsoft External Staff

2025-03-12T06:13:10.1433333+00:00

Hi @Ken Just-Ken ,

just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.

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GOLANG: No stacks found for "custom" on Azure Functions v4

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