Problem with auth to AWS MSK when profile has name in uppercase

[tc559]

on Mac OS (I didn't try to reproduce on Linux)
using

[profile DEV]
sso_session = main
sso_account_id = REDACTED
sso_role_name = Developer
region = eu-central-1
output = yaml

with

  kafka-dev:
    brokers:
      - b-2.redacted.kafka.eu-central-1.amazonaws.com:9098
      - b-1.redacted.kafka.eu-central-1.amazonaws.com:9098
    sasl:
      enabled: true
      mechanism: oauth
      tokenprovider:
        plugin: aws
        options:
          region: eu-central-1
          profile: DEV
          debug: true
    tls:
      enabled: true

Leads to auth failure. Changing profile name to lowercase makes it work.

[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: 2026/01/08 13:37:30 failed to get caller identity: operation error STS: GetCallerIdentity, https response error StatusCode: 403, RequestID: 520d38f4-c730-4fcf-9b1b-e673a28695fd, api error InvalidClientTokenId: The security token included in the request is invalid
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: panic: runtime error: invalid memory address or nil pointer dereference
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: [signal SIGSEGV: segmentation violation code=0x2 addr=0x10 pc=0x100e04c2c]
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: goroutine 51 [running]:
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: github.com/aws/aws-msk-iam-sasl-signer-go/signer.logCallerIdentity({0x10112f820, 0x101669f60}, {0x14000192cf0?, 0x0?}, {{0x140003d6482, 0x14}, {0x140003d64ad, 0x28}, {0x140003d64e8, 0x3f4}, ...})
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/aws/aws-msk-iam-sasl-signer-go@v1.0.4/signer/msk_auth_token_provider.go:377 +0x28c
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: github.com/aws/aws-msk-iam-sasl-signer-go/signer.constructAuthToken({0x10112f820, 0x101669f60}, {0x14000192cf0, 0xc}, 0x14000365880)
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/aws/aws-msk-iam-sasl-signer-go@v1.0.4/signer/msk_auth_token_provider.go:245 +0xe4
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: github.com/aws/aws-msk-iam-sasl-signer-go/signer.GenerateAuthTokenFromProfileWithSharedConfigFiles({0x10112f820, 0x101669f60}, {0x14000192cf0, 0xc}, {0x14000192d07?, 0x140003bc000?}, {0x0?, 0x100923cb8?, 0x4?})
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/aws/aws-msk-iam-sasl-signer-go@v1.0.4/signer/msk_auth_token_provider.go:66 +0x9c
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: github.com/aws/aws-msk-iam-sasl-signer-go/signer.GenerateAuthTokenFromProfile(...)
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/aws/aws-msk-iam-sasl-signer-go@v1.0.4/signer/msk_auth_token_provider.go:55
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: main.(*tokenProvider).Token(0x1400036e600)
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/deviceinsight/kafkactl-aws-plugin/main.go:82 +0x188
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: github.com/deviceinsight/kafkactl/v5/pkg/plugins/auth.(*TokenProviderRPCServer).Token(0x140001ef7b8?, {0x10090ce48?, 0x0?}, 0x14000315500)
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     github.com/deviceinsight/kafkactl/v5@v5.11.0/pkg/plugins/auth/plugin.go:51 +0x28
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: reflect.Value.call({0x1400036ecc0?, 0x14000306210?, 0x13?}, {0x100e53b17, 0x4}, {0x140003b6ef8, 0x3, 0x3?})
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     reflect/value.go:581 +0x960
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: reflect.Value.Call({0x1400036ecc0?, 0x14000306210?, 0x1?}, {0x14000277ef8?, 0x0?, 0x0?})
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     reflect/value.go:365 +0x94
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: net/rpc.(*service).call(0x14000317540, 0x1400031c8c0, 0x1400037c1e8, 0x1400037c200, 0x14000311200, 0x140001b5380, {0x101007f40?, 0x140003154e0?, 0x0?}, {0x100fb6ae0?, ...}, ...)
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     net/rpc/server.go:383 +0x1e8
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin: created by net/rpc.(*Server).ServeCodec in goroutine 39
[aws     ] 2026/01/08 13:37:30 [DEBUG] kafkactl-aws-plugin:     net/rpc/server.go:480 +0x284