HTTP API Gateway trailing slash - amazon-web-services

Question

I have an HTTP API Gateway which has a custom domain with mappings like https://api.example.com/myapi and one route POST / which triggers Lambda.
Problem is that https://api.example.com/myapi throws {"message": "Not Found"} and it working only with trailing slash https://api.example.com/myapi/.
How can I make it so it works with and without slash or in the worst case just without slash?
Here is CloudFormation for reference:
{
"Resources": {
"Webhoook6917ABA8": {
"Type": "AWS::Lambda::Function",
"Properties": {...}
},
"DomainNameEC95A6E9": {
"Type": "AWS::ApiGatewayV2::DomainName",
"Properties": {
"DomainName": "api.example.com",
"DomainNameConfigurations": [
{
"CertificateArn": "arn:***",
"EndpointType": "REGIONAL"
}
]
}
},
"ApiA2E3A7D3": {
"Type": "AWS::ApiGatewayV2::Api",
"Properties": {
"Name": "Api",
"ProtocolType": "HTTP"
}
},
"ApiDefaultStageE05BC5D1": {
"Type": "AWS::ApiGatewayV2::Stage",
"Properties": {
"ApiId": {
"Ref": "ApiA2E3A7D3"
},
"StageName": "$default",
"AutoDeploy": true
},
"DependsOn": [
"DomainNameEC95A6E9"
]
},
"ApiDefaultStageDomainName710CA621": {
"Type": "AWS::ApiGatewayV2::ApiMapping",
"Properties": {
"ApiId": {
"Ref": "ApiA2E3A7D3"
},
"DomainName": {
"Ref": "DomainNameEC95A6E9"
},
"Stage": "$default",
"ApiMappingKey": "myapi"
},
"DependsOn": [
"DomainNameEC95A6E9",
"ApiDefaultStageE05BC5D1"
]
},
"ApiPOSTHttpIntegrationcc27d9637eb8fbf5d8b41e5d3f4f4743D2E9B97B": {
"Type": "AWS::ApiGatewayV2::Integration",
"Properties": {
"ApiId": {
"Ref": "ApiA2E3A7D3"
},
"IntegrationType": "AWS_PROXY",
"IntegrationUri": {
"Fn::GetAtt": [
"Webhoook6917ABA8",
"Arn"
]
},
"PayloadFormatVersion": "2.0"
}
},
"ApiPOSTE756F840": {
"Type": "AWS::ApiGatewayV2::Route",
"Properties": {
"ApiId": {
"Ref": "ApiA2E3A7D3"
},
"RouteKey": "POST /",
"AuthorizationType": "NONE",
"Target": {
"Fn::Join": [
"",
[
"integrations/",
{
"Ref": "ApiPOSTHttpIntegrationcc27d9637eb8fbf5d8b41e5d3f4f4743D2E9B97B"
}
]
]
}
}
}
}
}