I cannot build the Language server on my ubuntu 18.04 container.

When I do ./build.sh
I get the following errors:

System.TypeLoadException: Could not resolve type with token 01000249
at (wrapper managed-to-native) System.Reflection.MonoMethodInfo:get_method_info (intptr,System.Reflect
ion.MonoMethodInfo&)
at System.Reflection.MonoMethodInfo.GetMethodInfo (System.IntPtr handle) [0x00000] in <8f2c484307284b5
1944a1a13a14c0266>:0
at System.Reflection.MonoMethod.GetPseudoCustomAttributes () [0x00002] in <8f2c484307284b51944a1a13a14
c0266>:0
at System.MonoCustomAttrs.GetPseudoCustomAttributes (System.Reflection.ICustomAttributeProvider obj, S
ystem.Type attributeType) [0x0000d] in <8f2c484307284b51944a1a13a14c0266>:0
at System.MonoCustomAttrs.IsDefined (System.Reflection.ICustomAttributeProvider obj, System.Type attributeType, System.Boolean inherit) [0x0003b] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Reflection.MonoMethod.IsDefined (System.Type attributeType, System.Boolean inherit) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0
at Microsoft.Internal.AttributeServices.IsAttributeDefined[T] (System.Reflection.ICustomAttributeProvider attributeProvider, System.Boolean inherit) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsExport (System.Reflection.ICustomAttributeProvider attributeProvider) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo+c__Iterator0.MoveNext () [0x001cd] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.Linq.Enumerable.Any[TSource] (System.Collections.Generic.IEnumerable1[T] source) [0x00018] in <63992662b765477a898ef49cdcc99ee2>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.HasExports () [0x0000c] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsPartDiscoverable () [0x0001d] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedModelDiscovery.CreatePartDefinitionIfDi Could not resolve type with token 01000249 System.TypeLoadException: Could not resolve type with token 01000249 at (wrapper managed-to-native) System.Reflection.MonoMethodInfo:get_method_info (intptr,System.Reflect ion.MonoMethodInfo&) at System.Reflection.MonoMethodInfo.GetMethodInfo (System.IntPtr handle) [0x00000] in <8f2c484307284b5 1944a1a13a14c0266>:0 at System.Reflection.MonoMethod.GetPseudoCustomAttributes () [0x00002] in <8f2c484307284b51944a1a13a14 c0266>:0 at System.MonoCustomAttrs.GetPseudoCustomAttributes (System.Reflection.ICustomAttributeProvider obj, S ystem.Type attributeType) [0x0000d] in <8f2c484307284b51944a1a13a14c0266>:0 at System.MonoCustomAttrs.IsDefined (System.Reflection.ICustomAttributeProvider obj, System.Type attributeType, System.Boolean inherit) [0x0003b] in <8f2c484307284b51944a1a13a14c0266>:0 at System.Reflection.MonoMethod.IsDefined (System.Type attributeType, System.Boolean inherit) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 at Microsoft.Internal.AttributeServices.IsAttributeDefined[T] (System.Reflection.ICustomAttributeProvider attributeProvider, System.Boolean inherit) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsExport (System.Reflection.ICustomAttributeProvider attributeProvider) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo+<GetExportMembers>c__Iterator0.MoveNext () [0x001cd] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.Linq.Enumerable.Any[TSource] (System.Collections.Generic.IEnumerable1[T] source) [0x00018] in <63992662b765477a898ef49cdcc99ee2>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.HasExports () [0x0000c] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsPartDiscoverable () [0x0001d] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedModelDiscovery.CreatePartDefinitionIfDi
Could not resolve type with token 01000249
System.TypeLoadException: Could not resolve type with token 01000249
at (wrapper managed-to-native) System.Reflection.MonoMethodInfo:get_method_info (intptr,System.Reflect
ion.MonoMethodInfo&)
at System.Reflection.MonoMethodInfo.GetMethodInfo (System.IntPtr handle) [0x00000] in <8f2c484307284b5
1944a1a13a14c0266>:0
at System.Reflection.MonoMethod.GetPseudoCustomAttributes () [0x00002] in <8f2c484307284b51944a1a13a14
c0266>:0
at System.MonoCustomAttrs.GetPseudoCustomAttributes (System.Reflection.ICustomAttributeProvider obj, S
ystem.Type attributeType) [0x0000d] in <8f2c484307284b51944a1a13a14c0266>:0
at System.MonoCustomAttrs.IsDefined (System.Reflection.ICustomAttributeProvider obj, System.Type attributeType, System.Boolean inherit) [0x0003b] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Reflection.MonoMethod.IsDefined (System.Type attributeType, System.Boolean inherit) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0
at Microsoft.Internal.AttributeServices.IsAttributeDefined[T] (System.Reflection.ICustomAttributeProvider attributeProvider, System.Boolean inherit) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsExport (System.Reflection.ICustomAttributeProvider attributeProvider) [0x00000] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo+c__Iterator0.MoveNext () [0x001cd] in <0007e672dd7f4959adc6f8103d9c843f>:0
at System.Linq.Enumerable.Any[TSource] (System.Collections.Generic.IEnumerable1[T] source) [0x00018] in <63992662b765477a898ef49cdcc99ee2>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.HasExports () [0x0000c] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedPartCreationInfo.IsPartDiscoverable () [0x0001d] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.AttributedModel.AttributedModelDiscovery.CreatePartDefinitionIfDiscoverable (System.Type type, System.ComponentModel.Composition.Primitives.ICompositionElement origin) [0x0000a] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.Hosting.TypeCatalog.get_PartsInternal () [0x00052] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.ComponentModel.Composition.Hosting.TypeCatalog.CreateIndex () [0x0000b] in <0007e672dd7f4959adc6f8103d9c843f>:0 at System.Lazy1[T].CreateValue () [0x00075] in <8f2c484307284b51944a1a13a14c0266>:0
Could not restore NuGet packages.

Description
We initially tried to install the theia-csharp-extension which does not work yet correctly / at all.
So we stumbled over this plugin as alternative.
We installed it manually and fortunately it worked perfectly (although the popup sometimes takes a few seconds).
The setup was quite easy, like 1. creating a plugin directory, 2. placing this plugin either compressed as .theia file or uncompressed into the plugin directory, 3. starting theia with an additional commandline argument telling it where to load additional plugins.

What's Expected
Here is a brief info, how we used this extension in our docker container:

ENV PLUGIN_OMNISHARP_NAME=omnisharp_theia_plugin
ENV PLUGIN_OMNISHARP_VERSION=v0.0.6
ENV PLUGIN_OMNISHARP_URL=https://github.com/redhat-developer/omnisharp-theia-plugin/releases/download/${PLUGIN_OMNISHARP_VERSION}/${PLUGIN_OMNISHARP_NAME}.theia

USER theia

WORKDIR /home/theia

RUN mkdir --parents                             \
          ./plugins                             \
 && wget --output-document=/tmp/plugin.theia    \
         ${PLUGIN_OMNISHARP_URL}                \
 && unzip /tmp/plugin.theia                     \
          -d ./plugins/${PLUGIN_OMNISHARP_NAME} \
 && rm --force                                  \
       /tmp/plugin.theia

Tool versions
yarn: 1.16.0
npm: 6.7.0
node: v11.15.0
os: Ubuntu 18.04.2 LTS Desktop